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Annual killifishes exhibit a number of unique life history characters including the occurrence of embryonic diapause, unique cell movements associated with dispersion and subsequent reaggregation of the embryonic blastomeres, and a short post-embryonic life span. Insulin-like growth factor (IGF) signaling is known to play a role in the regulation of metabolic dormancy in a number of animals but has not been explored in annual killifishes. The abundance of IGF proteins during development and the developmental effects of blocking IGF signaling by pharmacological inhibition of the insulin-like growth factor I receptor (IGF1R) were explored in embryos of the annual killifish Austrofundulus limnaeus Blocking of IGF signaling in embryos that would normally escape entrance into diapause resulted in a phenotype that was remarkably similar to that of embryos entering diapause. IGF-I protein abundance spikes during early development in embryos that will not enter diapause. In contrast, IGF-I levels remain low during early development in embryos that will enter diapause II. IGF-II protein is packaged at higher levels in escape-bound embryos compared with diapause-bound embryos. However, IGF-II levels quickly decrease and remain low during early development and only increase substantially during late development in both developmental trajectories. Developmental patterns of IGF-I and IGF-II protein abundance under conditions that would either induce or bypass entrance into diapause are consistent with a role for IGF signaling in the regulation of developmental trajectory and entrance into diapause in this species. We propose that IGF signaling may be a unifying regulatory pathway that explains the larger suite of characters that are associated with the complex life history of annual killifishes., Competing Interests: Competing interestsThe authors declare no competing or financial interests., (© 2017. Published by The Company of Biologists Ltd.)

Inhibition of histone deacetylases (HDACs) has emerged as a new target for cancer therapies. The present study examined the antitumor effect and molecular mechanism of the HDAC inhibitor apicidin in YD-15 human salivary mucoepidermoid carcinoma (MEC) cells. The cells were treated with apicidin and cell death was quantified using an MTT assay. Apoptosis and autophagy were measured using flow cytometry, immunoblot analysis and cell staining. Regulation of the signaling pathways was monitored using immunoblot analysis and co-treatment with specific inhibitors. Insulin-like growth factor 1 receptor (IGF-1R) was knocked down using specific siRNA. Apicidin significantly inhibited the proliferation of MEC cells. Apicidin also induced apoptosis through the inactivation of extracellular signal-regulated kinase (ERK) and AKT/mTOR signaling and activation of c-Jun NH2-terminal kinase (JNK), whereas apicidin promoted autophagy through inactivation of the AKT/mTOR signaling. These effects may be mediated by the inhibition of IGF-1R, an upstream regulator of MAPK and AKT/mTOR pathways. These results suggested that apicidin is an attractive chemotherapeutic agent against salivary MEC and may be a good candidate for targeting IGF-1R for cancer therapies.

Background: Several microRNAs (miRs) have been shown to regulate gene expression in the heart, and dysregulation of their expression has been linked to cardiac disease. miR-378 is strongly expressed in the mammalian heart but so far has been studied predominantly in cancer, in which it regulates cell survival and tumor growth., Methods and Results: Here, we report tight control of cardiomyocyte hypertrophy through miR-378. In isolated primary cardiomyocytes, miR-378 was found to be both necessary and sufficient to repress cardiomyocyte hypertrophy. Bioinformatic prediction suggested that factors of the mitogen-activated protein kinase (MAPK) pathway are enriched among miR-378 targets. Using mRNA and protein expression analysis along with luciferase assays, we validated 4 key components of the MAPK pathway as targets of miR-378: MAPK1 itself, insulin-like growth factor receptor 1, growth factor receptor-bound protein 2, and kinase suppressor of ras 1. RNA interference with these targets prevented the prohypertrophic effect of antimiR-378, suggesting their functional relation with miR-378. Because miR-378 significantly decreases in cardiac disease, we sought to compensate for its loss through adeno-associated virus-mediated, cardiomyocyte-targeted expression of miR-378 in an in vivo model of cardiac hypertrophy (pressure overload by thoracic aortic constriction). Restoration of miR-378 levels significantly attenuated thoracic aortic constriction-induced cardiac hypertrophy and improved cardiac function., Conclusions: Our data identify miR-378 as a regulator of cardiomyocyte hypertrophy, which exerts its activity by suppressing the MAPK signaling pathway on several distinct levels. Restoration of disease-associated loss of miR-378 through cardiomyocyte-targeted adeno-associated virus-miR-378 may prove to be an effective therapeutic strategy in myocardial disease.

Pathogens cause damage, and their elimination requires activation of the costly immune response. A highly economic defense strategy should thus be the behavioral avoidance of pathogens, as manifested in humans by all aspects of hygiene or revulsion at pathogen-rich material. Despite its potential importance, behavioral defenses have as yet received only little attention in biomedical research--in stark contrast to the physiological immune system. In the present study, the genetics of such behavioral defenses are elucidated in a simple model organism, the nematode Caenorhabditis elegans. We show for the first time that mutations in the insulin-like receptor (ILR) pathway lead to two distinct behavioral responses against pathogenic strains of the gram-positive bacterium Bacillus thuringiensis (BT), including the physical evasion of pathogens and their reduced oral uptake. Since this pathway also contributes to nematode stress resistance, the results surprisingly reveal a genetic link between physiological and behavioral defenses. Considering that many signaling pathways have conserved their functions across evolution, including the ILR pathway, this signaling cascade may represent an interesting candidate regulator for behavioral defenses in more complex organisms, including humans.

The mitogenic signaling in mammalian cells is carried out mainly by growth factors that interact with receptors localized at the plasma membrane. Most of these receptors have a tyrosine kinase activity domain that is localized at the cytoplasmic region of the molecule. The interaction of the growth factors with the receptors, besides inducing the kinase activity of the receptor, activate signaling pathways the alter gene expression patterns and induce mitogenesis, or if deregulated are related to cancer. Among these receptors ERBB, VEGF, PDGF and IGF are attractive targets for directed therapies. ERBB receptors are frequently involved in the production of many types of cancers. Both, the over-expression of the growth factor and the receptor, besides mutations at the cytoplasmic tyrosine kinase domain contribute to constitutive signaling in human cancer. VEGF has a pivotal role in maintaining the tumor growth by facilitating growth of new blood vessels. Therefore, inhibition of tumor growth targeting of the tumor vasculature, by interfering with the activity of VEGFr is now a real alternative in combinatorial therapies. PDGF is a growth factor involved in growth of connective tissue and wound healing. Activating mutations of PDGFr have been found in gastrointestinal tumors and the autocrine signaling maintained by this receptor have been described in many tumors. Imatinib, and inhibitor of the tyrosine kinase activity of Bcr-Abl targets also the kinase of the PDGFr. Finally IGF-I an II have an important antiapoptotic and pro-mitogenic role in most tumors. Different inhibitors are now under clinical studies for the use in combination of chemotherapeutic drugs in the treatment of different tumors.

The insulin-like growth factor (IGF) system plays a central role in the neuroendocrine regulation of growth in all vertebrates. Evidence from studies in a variety of vertebrate species suggest that this growth factor complex, composed of ligands, receptors, and high-affinity binding proteins, evolved early during vertebrate evolution. Among nonmammalian vertebrates, IGF signaling has been studied most extensively in fish, particularly teleosts of commercial importance. The unique life history characteristics associated with their primarily aquatic existence has fortuitously led to the identification of novel functions of the IGF system that are not evident from studies in mammals and other tetrapod vertebrates. Furthermore, the emergence of the zebrafish as a preferred model for development genetics has spawned progress in determining the requirements for IGF signaling during vertebrate embryonic development. This review is intended as a summary of our understanding of IGF signaling, as revealed through research into the expression, function, and evolution of IGF ligands, receptors, and binding proteins in fish.

Objective: We have shown previously that oxidized LDL decreases insulin-like growth factor-1 (IGF-1) and IGF-1 receptor expression in vascular smooth muscle cells and that IGF-1 and IGF-1 receptor expression are reduced in the deep intima of early atherosclerotic lesions. Because oxidized LDL is potentially important for the depletion of vascular smooth muscle cells contributing to plaque destabilization, we studied the role of IGF-1 in oxidized LDL-induced apoptosis., Methods and Results: We provide evidence that oxidized LDL-induced apoptosis is caused by decreased mitochondrial membrane potential and increased cytochrome C release in human aortic vascular smooth muscle cells. Overexpression of the IGF-1 receptor by using an adenovirus completely abrogated these effects. The antiapoptotic function of the IGF-1 receptor was associated with increased Akt kinase activity and increased expression of phosphorylated Bad. Moreover, a dominant-negative p85 phosphatidylinositol 3-kinase adenovirus blocked the capacity of the IGF-1 receptor to prevent oxidized LDL-induced apoptosis., Conclusions: Our data demonstrate that IGF-1 receptor activation inhibits oxidized LDL-induced cytochrome C release and apoptosis through the phosphatidylinositol 3-kinase/Akt signaling pathway and suggest that genetic or pharmacological activation of the IGF-1 receptor may be a useful strategy to stabilize atherosclerotic plaques.

The closely related proto-oncogene proteins CrkII and CrkL consist of one SH2 and two SH3 domains and share 60% overall homology with the highest identity within their functional domains. In this study we show that CrkL and CrkII may play overlapping but different roles in insulin-like growth factor (IGF)-I receptor-mediated signal transduction. While both proteins are substrates involved in IGF-I receptor signaling, they apparently demonstrate important different properties and different biological responses. Evidence supporting this hypothesis includes (a) the oncogenic potential of CrkL versus the absence of this potential in CrkII overexpressing cell lines, (b) the inhibition of IGF-I-dependent cell cycle progression by overexpression of CrkII, and (c) the differential regulation of the phosphorylation status of selective proteins in CrkII and CrkL overexpressing cell lines. In addition we demonstrate the specific association of CrkL and CrkII with the newly characterized IRS-4 protein, again in a differential manner. Whereas CrkL strongly interacts with IRS-4 via its SH2 and N-terminal SH3 domains, CrkII interacts only via its SH2 domain, possibly explaining the unstable nature of IRS-4-CrkII association. The results obtained allow us to propose a unique mechanism of CrkL and CrkII tyrosine phosphorylation in response to IGF-I stimulation. Thus these highly homologous proteins apparently possess structural features that allow for the differential association of each protein with different effector molecules, thereby activating different signaling pathways and resulting in unique biological roles of these proteins.

Several studies support the idea that the polypeptides belonging to the family of insulin and insulin-like growth factors (IGFs) play an important role in brain development and continue to be produced in discrete areas of the adult brain. In numerous neuronal populations within the olfactory bulb, the cerebral and cerebellar cortex, the hippocampus, some diencephalic and brainstem nuclei, the spinal cord and the retina, specific insulin and IGF receptors, as well as crucial components of the intracellular receptor signaling pathway have been demonstrated. Thus, mature neurons are endowed with the cellular machinery to respond to insulin and IGF stimulation. Studies in vitro and in vivo, using normal and transgenic animals, have led to the hypothesis that, in the adult brain, IGF-I not only acts as a trophic factor, but also as a neuromodulator of some higher brain functions, such as long-term potentiation and depression. Furthermore, a trophic effect on certain neuronal populations becomes clearly evident in the ischemic brain or neurodegenerative disorders. Thus, the analysis of the early intracellular signaling pathway for the insulin/IGF receptor family in the brain is providing us with new intriguing findings on the way the mammalian brain is sculpted and operates.

To survey and compare the signaling pathways from the insulin and insulin-like growth factor-I (IGF-I) receptors in undifferentiated and differentiated muscle cells, we examined the phosphotyrosine (Ptyr)-containing polypeptides elicited in L6 and Sol8 myoblasts and myotubes by the combination of insulin and IGF-I. These polypeptides were detected by immunoblotting with antibodies against Ptyr. In the L6 myoblasts and myotubes and the Sol8 myoblasts, Ptyr polypeptides of approximately 240, 175, 115, 100, 41, and 37 kilodaltons (kDa) appeared in response to insulin-IGF-I. With the Sol8 myotubes, the 240-, 175-, and 37-kDa Ptyr polypeptides were detected in basal cells, and only the Ptyr content of the 175-kDa one increased in response to insulin-IGF-I. The polypeptides of 175, 41, and 37 kDa were tentatively identified as the insulin receptor substrate 1 (IRS1) and extracellular signal-regulated kinases 1 and 2 (ERK1 and -2), respectively, by immunoblotting with antibodies specific for these proteins, and the 115- and 100-kDa polypeptides are probably the beta-subunits of the insulin and IGF-I receptors. The amounts of IRS1, ERK1, and ERK2 were roughly the same in the L6 and Sol8 myoblasts and myotubes. Thus, differentiation of the myoblasts to myotubes was not accompanied by the detectable appearance of new insulin-IGF-I-elicited Ptyr polypeptides or marked changes in the amounts of known participants in their signaling pathways.