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Therapeutic resistance in recurrent glioblastoma multiforme (GBM) after concurrent chemoradiotherapy (CCRT) is a challenging issue. Although standard fractionated radiation is essential to treat GBM, it has led to local recurrence along with therapy-resistant cells in the ionizing radiation (IR) field. Lines of evidence showed cancer stem cells (CSCs) play a vital role in therapy resistance in many cancer types, including GBM. However, the molecular mechanism is poorly understood. Here, we proposed that autophagy could be involved in GSC induction for radioresistance. In a clinical setting, patients who received radiation/chemotherapy had higher LC3II expression and showed poor overall survival compared with those with low LC3 II. In a cell model, U87MG and GBM8401 expressed high level of stemness markers CD133, CD44, Nestin, and autophagy marker P62/LC3II after receiving standard fractionated IR. Furthermore, Wnt/β-catenin proved to be a potential pathway and related to P62 by using proteasome inhibitor (MG132). Moreover, pharmacological inhibition of autophagy with BAF and CQ inhibit GSC cell growth by impairing autophagy flux as demonstrated by decrease Nestin, CD133, and SOX-2 levels. In conclusion, we demonstrated that fractionated IR could induce GSCs with the stemness phenotype by P62-mediated autophagy through the Wnt/β-catenin for radioresistance. This study offers a new therapeutic strategy for targeting GBM in the future.

We previously reported that Aurora-A and the hNinein binding protein AIBp facilitate centrosomal structure maintenance and contribute to spindle formation. Here, we report that AIBp also interacts with Plk1, raising the possibility of functional similarity to Bora, which subsequently promotes Aurora-A–mediated Plk1 activation at Thr210 as well as Aurora-A activation at Thr288. In kinase assays, AIBp acts not only as a substrate but also as a positive regulator of both Aurora-A and Plk1. However, AIBp functions as a negative regulator to block phosphorylation of hNinein mediated by Aurora-A and Plk1. These findings suggest a novel AIBp-dependent regulatory machinery that controls mitotic entry. Additionally, knockdown of hNinein caused failure of AIBp to target the centrosome, whereas depletion of AIBp did not affect the localization of hNinein and microtubule nucleation. Notably, knockdown of AIBp in HeLa cells impaired both Aurora-A and Plk1 kinase, resulting in phenotypes with multiple spindle pole formation and chromosome misalignment. Our data show that depletion of AIBp results in the mis-localization of TACC3 and ch-TOG, but not CEP192 and CEP215, suggesting that loss of AIBp dominantly affects the Aurora-A substrate to cause mitotic aberrations. Collectively, our data demonstrate that AIBp contributes to mitotic entry and bipolar spindle assembly and may partially control localization, phosphorylation, and activation of both Aurora-A and Plk1 via hNinein during mitotic progression.

Based on the protein kinase A (PKA)/GSK3&beta, interaction protein (GSKIP)/glycogen synthase kinase 3&beta, (GSK3&beta, ) axis, we hypothesized that these might play a role in Tau phosphorylation. Here, we report that the phosphorylation of Tau Ser409 in SHSY5Y cells was increased by overexpression of GSKIP WT more than by PKA- and GSK3&beta, binding defective mutants (V41/L45 and L130, respectively). We conducted in vitro assays of various kinase combinations to show that a combination of GSK3&beta, with PKA but not Ca2+/calmodulin-dependent protein kinase II (CaMK II) might provide a conformational shelter to harbor Tau Ser409. Cerebrospinal fluid (CSF) was evaluated to extend the clinical significance of Tau phosphorylation status in Alzheimer&rsquo, s disease (AD), neurological disorders (NAD), and mild cognitive impairment (MCI). We found higher levels of different PKA&ndash, Tau phosphorylation sites (Ser214, Ser262, and Ser409) in AD than in NAD, MCI, and normal groups. Moreover, we used the CRISPR/Cas9 system to produce amyloid precursor protein (APPWT/D678H) isogenic mutants. These results demonstrated an enhanced level of phosphorylation by PKA but not by the control. This study is the first to demonstrate a transient increase in phosphor-Tau caused by PKA, but not GSK3&beta, in the CSF and induced pluripotent stem cells (iPSCs) of AD, implying that both GSKIP and GSK3&beta, function as anchoring proteins to strengthen the cAMP/PKA/Tau axis signaling during AD pathogenesis.

Mitochondrial fission and fusion cycles are integrated with cell cycle progression. Here we first re-visited how mitochondrial ETC inhibition disturbed mitosis progression, resulting in multipolar spindles formation in HeLa cells. Inhibitors of ETC complex I (rotenone, ROT) and complex III (antimycin A, AA) decreased the phosphorylation of Plk1 T210 and Aurora A T288 in the mitotic phase (M-phase), especially ROT, affecting the dynamic phosphorylation status of fission protein dynamin-related protein 1 (Drp1) and the Ser637/Ser616 ratio. We then tested whether specific Drp1 inhibitors, Mdivi-1 or Dynasore, affected the dynamic phosphorylation status of Drp1. Similar to the effects of ROT and AA, our results showed that Mdivi-1 but not Dynasore influenced the dynamic phosphorylation status of Ser637 and Ser616 in Drp1, which converged with mitotic kinases (Cdk1, Plk1, Aurora A) and centrosome-associated proteins to significantly accelerate mitotic defects. Moreover, our data also indicated that evoking mito-Drp1-Ser637 by protein kinase A (PKA) rather than Drp1-Ser616 by Cdk1/Cyclin B resulted in mitochondrial fission via the PINK1/Parkin pathway to promote more efficient mitophagy and simultaneously caused multipolar spindles. Collectively, this study is the first to uncover that mito-Drp1-Ser637 by PKA, but not Drp1-Ser616, drives mitophagy to exert multipolar spindles formation during M-phase.

Bcl2L12 as a new member of the Bcl2 family, which contains a BH2 domain and shares a lower amino acid similarity with other Bcl2 family proteins. Bcl2L12 is reported to be involved in apoptosis regulation, but this role remains controversial in different cancer type. Temozolomide (TMZ) is currently used to intervene glioma multiforme (GBM), but an acquired chemotherapeutic resistance maybe occurred due to undesired autophagy. Previous studies uncovered that Bcl2L12 may interact with Bcl-xL and may harbor a BH3-like domain. Therefore, we investigated whether this BH3-like domain is responsible for the Bcl2L12 anti-apoptotic property. Moreover, we tested whether ABT-737, a BH3 mimetic agent, can be combined with TMZ to treat GBM. We aligned Bcl2L12 with Bcl2 family members, compared interacting pattern of BH3 domain and their protein 3D structure. We identified that Bcl2L12 interacts with Bcl-xL and Bcl2 in yeast two-hybrid system. Bcl2L12192-220 was a minimal region for Bcl2L12-Bcl-xL interaction. Five-point mutations with respect to hydrophobic and charge residues were generated to test whether they are the key residue of BH3-like domain. Our data showed that both h1 (L213) and h2 residue (L217) are essential for Bcl2L12 interacting with Bcl2 family proteins. Ectopically expressed h1 or h2 mutant in U87MG cell line resulted in reactivation of cleaved-PARP, caspase-3 and cytochrome c releasing compared to Bcl2L12 wt group. Implementing ABT-737 combined with TMZ provided a superior effect on apoptosis induction in Bcl2L12 wt group, which effectively reactivated apoptotic markers. Altogether, our findings indicated that Bcl2L12 retains a BH3-like domain, which is important for the Bcl2L12 anti-apoptotic property and TMZ-induced autophagy. Our results basically support the idea of using ABT-737 to counteract the anti-apoptotic role of Bcl2L12 and sensitize drug response of the GBM cells to TMZ.

GSK3β interacting protein (GSKIP) is a naturally occurring negative regulator of GSK3β and retains both the Protein Kinase A Regulatory subunit binding (PKA-RII) domain and GSK3β interacting domain. Of these two domains, we found that PKA-RII is required for forming a working complex comprising PKA/GSKIP/GSK3β/Drp1 to influence phosphorylation of Drp1 Ser637. In this study, bioinformatics and experimental explorations re-analyzing GSKIP's biofunctions suggest that the evolutionarily conserved Domain of Unknown Function (DUF727) is an ancestral prototype of GSKIP in prokaryotes, and acquired the C-terminal GSK3β binding site (tail) in invertebrates except for Saccharomyces spp., after which the N-terminal PKA-RII binding region (head) evolved in vertebrates. These two regions mutually influence each other and modulate GSKIP binding to GSK3β in yeast two-hybrid assays and co-immunoprecipitation. Molecular modeling showed that mammalian GSKIP could form a dimer through the L130 residue (GSK3β binding site) rather than V41/L45 residues. In contrast, V41/L45P mutant facilitated a gain-of-function effect on GSKIP dimerization, further influencing binding behavior to GSK3β compared to GSKIP wild-type (wt). The V41/L45 residues are not only responsible for PKA RII binding that controls GSK3β activity, but also affect dimerization of GSKIP monomer, with net results of gain-of-function in GSKIP-GSK3β interaction. In addition to its reported role in modulating Drp1, Ser637 phosphorylation caused mitochondrial elongation; we postulated that GSKIP might be involved in the Wnt signaling pathway as a scavenger to recruit GSK3β away from the β-catenin destruction complex and as a competitor to compete for GSK3β binding, resulting in accumulation of S675 phosphorylated β-catenin.

Glioblastoma multiforme is one of the most serious malignant brain tumors and is characterized by resistance to chemotherapy and radiation therapy. Recent studies suggest that autophagy may play an important role not only in the regulation of cancer development and progression but also in determining the response of cancer cells to anticancer therapy. The purpose of the present study was to assess the relationship between protein expressions of two autophagy markers, LC3B and Beclin-1, with clinical parameters in astrocytoma patients. Furthermore, the expression of CD133, a marker of the cancer stem-like cells, in astrocytoma patients was also investigated. A total of 106 thin-section slides were retrospectively collected from astrocytoma patients. LC3B, but not Beclin-1, protein expression was found to significantly correlate with resistance to radiation- or chemotherapy. In addition, high intensity of LC3B staining was predictive of poor prognosis. Furthermore, survival time of patients with high-level expression in both CD133 and LC3B was significantly shorter than those with weak expression in both CD133 and LC3B. These results suggest that astrocytoma cancer stem-like cells together with enhanced autophagy may cause resistance to radiation therapy/chemotherapy and that targeting the cancer stem-like cell in astrocytoma may offer a viable therapeutic approach.

Cerebral vasospasm is the leading cause of mortality and morbidity in patients after aneurysmal subarachnoid hemorrhage (SAH). However, the mechanism and adequate treatment of vasospasm are still elusive. In the present study, we evaluate the effect and possible mechanism of progesterone on SAH-induced vasospasm in a two-hemorrhage rodent model of SAH. Progesterone (8 mg/kg) was subcutaneously injected in ovariectomized female Sprague-Dawley rats one hour after SAH induction. The degree of vasospasm was determined by averaging the cross-sectional areas of basilar artery 7 days after first SAH. Expressions of endothelial nitric oxide synthase (eNOS) and phosphorylated Akt (phospho-Akt) in basilar arteries were evaluated. Prior to perfusion fixation, there were no significant differences among the control and treated groups in physiological parameters recorded. Progesterone treatment significantly(P<0.01)attenuated SAH-induced vasospasm. The SAH-induced suppression of eNOS protein and phospho-Akt were relieved by progesterone treatment. This result further confirmed that progesterone is effective in preventing SAH-induced vasospasm. The beneficial effect of progesterone might be in part related to upregulation of expression of eNOS via Akt signaling pathway after SAH. Progesterone holds therapeutic promise in the treatment of cerebral vasospasm following SAH.

Transforming growth factor-beta 1 (TGF-β1) has been reported to be a possible marker for a number of tumors, including brain tumors. The aim of this study was to measure the plasma levels of TGF-β1 in patients with low- and high-grade astrocytomas before and after surgery. This prospective study included 14 patients with low-grade astrocytomas and 25 with high-grade astrocytomas who underwent tumor removal and 13 controls (patients who underwent cranioplasty for skull bone defects). Plasma levels of TGF-β1 were measured in all subjects using enzyme-linked immunosorbent assay (ELISA). Receiver operating characteristic (ROC) curve analysis showed that when the level of TGF-β1 before tumor removal was ≥ 2.52 ng/ml, astrocytoma was predicted with a sensitivity of 94.9% and specificity of 100%. The mean plasma level of TGF-β1 in both the low-grade and high-grade astrocytoma groups significantly decreased after tumor removal (p0.05); there was no significant change in TGF-β1 plasma level of the controls following surgery. Patients with high-grade astrocytomas had a significantly higher mortality rate than patients with low-grade astrocytomas (p=0.019) and significantly shorter survival (p=0.008). A positive correlation between TGF-β1 level after tumor removal and tumor volume was only found in the high-grade astrocytoma group (γ=0.597, p=0.002). The findings show that plasma TGF-β1 level was increased in patients with low-grade and high-grade astrocytoma, and that the levels significantly decreased after tumor removal in both groups. The results provide additional evidence that TGF-β1 might be useful as a tumor marker for astrocytomas.

Dysregulated centrosomal expression has been observed in high grade gliomas. Thus, this study aimed to examine the expression of Aurora family kinase and various centrosomal proteins, including centrin, γ-tubulin, and hNinein isoforms, in human brain tumors, including 29 meningiomas, 34 astrocytomas, 6 pituitary adenomas, and 6 metastatic tumors. mRNA expression was evaluated using reverse transcription polymerase chain reaction. The role of hNinein isoform 6 expression in cell differentiation was assessed in BrdU-treated IMR-32 cells. Differential expression of centrosomal proteins of brain tumors and cell lines was observed. Specifically, centrin 2 and centrin 3 expression levels were classified as moderate or abundant in >97% of samples in the meningioma group, 63% of astrocytomas, >83% of metastatic and pituitary tumors. Alternatively, hNinein isoform 6 expression was only detected in normal brain and astrocytoma tumors (17/34); however, it was not expressed in meningioma (0/29), metastatic tumors (0/6) (P < 0.001). Of the six neuroblastoma cell lines analyzed only IMR-32 cells expressed hNinein isoform 6. Furthermore, downregulated expression of hNinein isoform 6 and upregulation of γ-tubulin was correlated to astrocytoma tumor grade (P < 0.001). Increased hNinein isoform 6 mRNA expression was observed in response to BrdU treatment, and its expression was greater in teratomas as compared to embryonic stem cells. Further studies are necessary to determine if hNinein isoform 6 functions as a tumor-suppressor gene in brain tumors. Differential centrosomal protein expression may result in altered centrosome function that is observed the in progression of various brain tumors. © 2012 International Union of Biochemistry and Molecular Biology, Inc.

BCL2L12 has been reported to be involved in post-mitochondrial apoptotic events in glioblastoma, but the role of BCL2L12A, a splicing variant of BCL2L12, remains unknown. In this study, we showed that BCL2L12 and BCL2L12A were overexpressed in glioblastoma multiforme (GBM). Large-scale yeast two-hybrid screening showed that BCL2L12 was a GSK3b binding partner in a testis cDNA library. Our data demonstrated that GSK3b interacts with BCL2L12 but not BCL2L12A, whose C terminus lacks a binding region. We found that a BCL2L12(153-191) fragment located outside of the C-terminal BH2 motif is responsible for GSK3b binding. In contrast, no interaction was detected between BCL2L12A and GSK3b. In vitro kinase and l-phosphatase assays showed that GSK3b phosphorylates BCL2L12 at S156, while this site is absent on BCL2L12A. Moreover, our data also showed that the BCL2L12(153-191) fragment directly interrupted GSK3bmediated Tau phosphorylation in a dose-dependent manner. Ectopic expression of GFP-fused BCL2L12 or BCL2L12A in U87MG cells leads to repression of apoptotic markers and protects against staurosporine (STS) insults, indicating an antiapoptotic role for both BCL2L12 and BCL2L12A. In contrast, no anti-apoptotic ability was seen in BCL2L12(S156A). When BCL2L12-expressing U87MG cells were co-administrated with STS and LiCl, cells underwent apoptosis. This effect could be reversed by LiCl. In short, we established a model to demonstrate that GSK3b interacts with and phosphorylates BCL2L12 and might also affect BCL2L12A to modulate the apoptosis signaling pathway in glioblastoma. These findings suggest that LiCl may be a prospective therapeutic agent against GBM.

Multiple phosphorylation sites of Drp1 have been characterized for their functional importance. However, the functional consequence of GSK3beta-mediated phosphorylation of Drp1 remains unclear. In this report, we pinpointed 11 Serine/Threonine sites spanning from residue 634~736 of the GED domain and robustly confirmed Drp1 Ser693 as a novel GSK3beta phosphorylation site. Our results suggest that GSK3beta-mediated phosphorylation at Ser693 does cause a dramatic decrease of GTPase activity; in contrast, GSK3beta-mediated phosphorylation at Ser693 appears not to affect Drp1 inter-/intra-molecular interactions. After identifying Ser693 as a GSK3beta phosphorylation site, we also determined that K679 is crucial for GSK3beta-binding, which strongly suggests that Drp1 is a novel substrate for GSK3beta. Thereafter, we found that overexpressed S693D, but not S693A mutant, caused an elongated mitochondrial morphology which is similar to that of K38A, S637D and K679A mutants. Interestedly, using H89 and LiCl to inhibit PKA and GSK3beta signaling, respectively, it appears that a portion of the elongated mitochondria switched to a fragmented phenotype. In investigating the biofunctionality of phosphorylation sites within the GED domain, cells overexpressing Drp1 S693D and S637D, but not S693A, showed an acquired resistance to H(2)O(2)-induced mitochondrial fragmentation and ensuing apoptosis, which affected cytochrome c, capase-3, -7, and PARP, but not LC3B, Atg-5, Beclin-1 and Bcl2 expressions. These results also showed that the S693D group is more effective in protecting both non-neuronal and neuronal cells from apoptotic death than the S637D group. Altogether, our data suggest that GSK3beta-mediated phosphorylation at Ser693 of Drp1 may be associated with mitochondrial elongation via down-regulating apoptosis, but not autophagy upon H(2)O(2) insult.

Cerebral vasospasm following subarachnoid hemorrhage (SAH) has been studied in terms of a contraction of the major cerebral arteries, but the effect of cerebrum tissue in SAH is not yet well understood. To gain insight into the biology of SAH-expressing cerebrum, we employed oligonucleotide microarrays to characterize the gene expression profiles of cerebrum tissue at the early stage of SAH. Functional gene expression in the cerebrum was analyzed 2 h following stage 1-hemorrhage in Sprague-Dawley rats. mRNA was investigated by performing microarray and quantitative real-time PCR analyses, and protein expression was determined by Western blot analysis. In this study, 18 upregulated and 18 downregulated genes displayed at least a 1.5-fold change. Five genes were verified by real-time PCR, including three upregulated genes [prostaglandin E synthase (PGES), CD14 antigen, and tissue inhibitor of metalloproteinase 1 (TIMP1)] as well as two downregulated genes [KRAB-zinc finger protein-2 (KZF-2) and γ-aminobutyric acid B receptor 1 (GABA B receptor)]. Notably, there were functional implications for the three upregulated genes involved in the inflammatory SAH process. However, the mechanisms leading to decreased KZF-2 and GABA B receptor expression in SAH have never been characterized. We conclude that oligonucleotide microarrays have the potential for use as a method to identify candidate genes associated with SAH and to provide novel investigational targets, including genes involved in the immune and inflammatory response. Furthermore, understanding the regulation of MMP9/TIMP1 during the early stages of SAH may elucidate the pathophysiological mechanisms in SAH rats.

Centrosomes are organelles involved in the organization of the mitotic spindle and may also be the targets of autoantibodies in autoimmune diseases. Human Ninein (hNinein) is a centrosomal autoantigen that is identified by autoimmune patient sera. However, none of the hNinein-specific fragments recognized by the autoantibodies in rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE) sera have been thoroughly characterized. We thus attempted to identify the fine specificity within the hNinein protein. In this study, four recombinant proteins in two isoforms of hNinein were used as autoantigens along with immunoassays as a molecular tool to investigate the prevalence of hNinein autoreactivity and its specificity in 22 RA and 32 SLE autoimmune disease sera. The data indicated a 50% higher prevalence of isoform 4 hNinein N-terminal autoantibodies in RA sera, whereas 22% of SLE patients were autoreactive to the N-terminal of isoform 4 hNinein compared to only a small percentage of autoreactive normal sera (5%). These results showed that autoepitopes on autoantigen hNinein are restricted to the N-terminal region and that a more significant proportion of RA patients exhibited centrosome reactivity.

The hedgehog (Hh) transcription factor Gli induces transformation of epithelial cells via induction of Snail, a repressor of E-cadherin. Epithelial-mesenchymal transition is also a determinant of the progression of tumorigenesis, following down-regulation of E-cadherin. However, the role of Hh signaling components and Snail/E-cadherin in brain tumors is not yet fully understood. We analyzed the expression of Hh signaling components and Snail/E-cadherin in 69 brain tumors by reverse transcription-polymerase chain reaction (RT-PCR). The data showed that overexpression of Smo (35/69), Ptch (50/69), Gli1 (56/69), Gli2 (29/69) and N-myc (39/69) might contribute to brain tumorigenesis. Our results also indicated that Snail and E-cadherin showed opposing expression in malignant tumors (high grade astrocytoma and metastasis). Snail and E-cadherin showed less correlation in benign brain tumors. We further investigated mutations of Gli2 and Snail by RT-PCR and direct sequencing. No mutation was observed on Gli2 but several sporadic mutations on Snail were found, including S96G, S111L, S111L/ S119Y and one nonsense mutation at codon 158 (Y158*) . An in vitro E-cadherin promoter assay showed that S96G, S111L, S111L/S119Y Snail mutants were decreased by 15, 25 and 50%, respectively, whereas Y158 * was increased by 40% compared to wild-type. Furthermore, our data showed that wild-type Snail and S96G, S 111L, S111L/S119Y translocated to the nucleus, while the Y158 * mutant failed to translocate to the nucleus. Taken together, our results demonstrate that Hh signaling components, the expression and mutations of Snail and the expression of E-cadherin may play an important role in human brain tumorigenesis.

Aurora-A is involved in chromosome alignment, centrosome maturation, mitotic spindle assembly and regards to an oncogene. Aurora-A is also known to bind to several other proteins affecting its up-regulation or down-regulation and localization. However, how these different binding signals work together to regulate Aurora-A is not properly known. To explore more Aurora-A interacting proteins, the low-copy yeast two-hybrid screening using Aurora-A as bait protein was performed. One novel gene, AIBp, was demonstrated to associate with Aurora-A by the yeast two-hybrid method and in vitro GST pull-down assay. Molecular characterization showed that AIBp possessed a binding site at the C-terminal with Aurora-A (kinase domain). Interestingly, AIBp also interacts with hNinein at the N-terminal, which overlaps with a previously reported hNinein and GSK3beta binding site. Using a kinase assay, AIBp interacts with the Aurora-A kinase domain functions as a positive regulator, whereas AIBp binding to hNinein appears to block the phosphorylation of hNinein by both Aurora-A and GSK3beta. siRNA-mediated elimination of AIBp from HeLa cells, results in a doughnut-like shape, asymmetrical spindle pole and multiple spindle pole formation. We also demonstrated that both AIBp and Aurora-A are co-overexpressed in various brain tumors. These studies demonstrate that AIBp may not only be required for the dynamic movement of Aurora-A at the centrosomes and spindle apparatus during the cell cycle, but may also be important during brain tumorigenesis.

Background High-grade gliomas have poor prognosis, requiring aggressive treatment. The aim of this study is to explore mitotic and centrosomal dysregulation in gliomas, which may provide novel targets for treatment. Methods A case-control study was performed using 34 resected gliomas, which were separated into low- and high-grade groups. Normal human brain tissue was used as a control. Using immunohistochemical analysis, immunofluorescent microscopy, and RT-PCR, detection of centrins 1 and 2, γ-tubulin, hNinein, Aurora A, and Aurora B, expression was performed. Analysis of the GBM8401 glioma cell line was also undertaken to complement the in vivo studies. Results In high-grade gliomas, the cells had greater than two very brightly staining centrioles within large, atypical nuclei, and moderate-to-strong Aurora A staining. Comparing with normal human brain tissue, most of the mRNAs expression in gliomas for centrosomal structural proteins, including centrin 3, γ-tubulin, and hNinein isoforms 1, 2, 5 and 6, Aurora A and Aurora B were elevated. The significant different expression was observed between high- and low-grade glioma in both γ-tubulin and Aurora A mRNA s. In the high-grade glioma group, 78.6% of the samples had higher than normal expression of γ-tubulin mRNA, which was significantly higher than in the low-grade glioma group (18.2%, p < 0.05). Conclusions Markers for mitotic dysregulation, such as supernumerary centrosomes and altered expression of centrosome-related mRNA and proteins were more frequently detected in higher grade gliomas. Therefore, these results are clinically useful for glioma staging as well as the development of novel treatments strategies.

The specificity and regulation of GSK3beta are thought to involve in the docking interactions at core kinase domain because of the particular amino acid residues. Recent X-ray diffraction studies illuminated the relative binding residues on AxinGID and FRATtide for GSK3beta docking and appeared that GSK3beta Val267Gly (V267G) and Tyr288Phe (Y288F) could distinguish the direct interaction between AxinGID and FRATtide. In order to explore the mode that involved the binding of GSKIP to GSK3beta and compare it with that of AxinGID and FRATtide, we pinpointed the binding sites of GSKIP to GSK3beta through the single-point mutation of four corresponding sites within GSK3beta (residues 260-300) as scaffold-binding region I (designated SBR-I(260-300)). Our data showed that these three binding proteins shared similar binding sites on GSK3beta. We also found that the binding of GSK3beta V267G mutant to GSKIP and AxinGID, but not that of Y288F mutant (effect on FRATtide), was affected. Further, based on the simulation data, the electron-density map of GSKIPtide bore closer similarity to the map AxinGID than to that of FRATtide. Interestingly, many C-terminal helix region point-mutants of GSK3beta L359P, F362A, E366K, and L367P were able to eliminate the binding with FRATtide, but not AxinGID or GSKIP. In addition, CABYR exhibited a unique mode in binding to C-terminal helix region of GSK3beta. Taken together, our data revealed that in addition to the core kinase domain, SBR-I(260-300), another novel C-terminus helix region, designated SBR-II(339-383), also appeared to participate in the recognition and specificity of GSK3beta in binding to other specific proteins.

Although prominent FRAT/GBP exhibits a limited degree of homology to Axin, the binding sites on GSK3 for FRAT/GBP and Axin may overlap to prevent the effect of FRAT/GBP in stabilizing beta-catenin in the Wnt pathway. Using a yeast two-hybrid screen, we identified a novel protein, GSK3beta interaction protein (GSKIP), which binds to GSK3beta. We have defined a 25-amino acid region in the C-terminus of GSKIP that is highly similar to the GSK3beta interaction domain (GID) of Axin. Using an in vitro kinase assay, our results indicate that GSKIP is a good GSK3beta substrate, and both the full-length protein and a C-terminal fragment of GSKIP can block phosphorylation of primed and nonprimed substrates in different fashions. Similar to Axin GID(381-405) and FRATtide, synthesized GSKIPtide is also shown to compete with and/or block the phosphorylation of Axin and beta-catenin by GSK3beta. Furthermore, our data indicate that overexpression of GSKIP induces beta-catenin accumulation in the cytoplasm and nucleus as visualized by immunofluorescence. A functional assay also demonstrates that GSKIP-transfected cells have a significant effect on the transactivity of Tcf-4. Collectively, we define GSKIP as a naturally occurring protein that is homologous with the GSK3beta interaction domain of Axin and is able to negatively regulate GSK3beta of the Wnt signaling pathway.