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Chaperone-mediated autophagy (CMA), one of the degradation pathways of proteins, is highly selective to substrates that have KFERQ-like motif. In this process, the substrate proteins are first recognized by the chaperone protein, heat shock cognate protein 70 (Hsc70), then delivered to lysosomal membrane surface where the single-span lysosomal receptor, lysosome-associated membrane protein type 2A (LAMP2A) can bind to the substrate proteins to form a 700 kDa protein complex that allows them to translocate into the lysosome lumen to be degraded by the hydrolytic enzymes. This degradation pathway mediated by CMA plays an important role in regulating glucose and lipid metabolism, transcription, DNA reparation, cell cycle, cellular response to stress and consequently, regulating many aging-associated human diseases, such as neurodegeneration, cancer and metabolic disorders. In this review, we provide an overview of current research on the functional roles of CMA primarily from a perspective of understanding and treating human diseases and also discuss its potential applications for diseases.

Heightened activity of glycogen synthase kinase-3β (GSK-3β) is linked to the degeneration of dopaminergic neurons in Parkinson's disease (PD). Phytic acid (PA), a naturally occurring compound with potent antioxidant property, has been shown to confer neuroprotection on dopaminergic neurons in PD. However, the underlying mechanism remains unclear. In the present study, MPTP and MPP+ treatments were used to model PD in mice and SH-SY5Y cells, respectively. We observed reduced tissue dopamine, disrupted synaptic vesicle recycling, and defective neurotransmitter exocytosis. Furthermore, expression of GSK-3β was upregulated while that of β-catenin was downregulated, concentration of cytosolic calcium was increased, and expressions of two dopamine carriers, dopamine transporter (DAT) and vesicular monoamine transporter 2 (VMAT2) were decreased. PA treatment attenuated the MPTP-induced upregulation of GSK-3β, increase in cytosolic calcium concentration, decreases in the levels of DAT, VMAT2, tissue dopamine, and synaptic vesicle recycling. Importantly, disturbances in synaptic vesicle recycling are thought to be early events in PD pathology. These findings suggest that PA is a promising therapeutic agent to treat early events in PD.

Isatin has been shown to initiate apoptotic processes in SH‑SY5Y neuroblastoma cells. The aim of the present study was to investigate whether isatin is also able to alter the proliferation and migratory ability of SH‑SY5Y cells. The results demonstrated that the proportion of SH‑SY5Y cells in G1 phase was significantly increased following treatment with isatin for 48 h with simultaneous downregulation of cyclin D1 expression. In addition, isatin significantly inhibited cell migration and invasion, along with decreases in matrix metalloproteinase (MMP)2 and MMP9 expression. In addition, isatin reduced the levels of phosphorylated signal transducer and activator of transcription 3 (p‑STAT3) in a concentration-dependent manner. These results demonstrated that isatin induces G1‑phase arrest in SH‑SY5Y cells, possibly by decreasing cyclin D1 expression as well as inhibiting their migration and invasiveness, probably by reducing MMP2 and MMP9. These effects may be exerted by isatin via a downregulating the levels of pSTAT3.

The purpose of this study was to investigate the anti-tumor effects of the isatin in vitro and in vivo. Human neuroblastoma cells (SH-SY5Y) were exposed to isatin at various concentrations (0, 50, 100, 200 μmol/l) for 48 h. Bcl-2 and Bax mRNA were analyzed via RT-PCR. Bcl-2, Bax, the inhibitor of caspase-activated DNase (ICAD) and cytochrome c protein were analyzed via western blot. Apoptosis, caspase-9, 3 activation and mitochondrial depolarization were assayed by flow cytometry. SH-SY5Y cells were injected into the right side of the mouse armpit. When the neoplasm was detected, the nude mice were randomly divided into four groups and received an injection of DMEM (negative control), 25 or 50mg/kg isatin, or cyclophosphamide (positive control). The inhibitory effects of isatin on the murine xenograft were determined using a growth curve and Bcl-2 and Bax mRNA and protein were studied using RT-PCR and western blot, respectively. The results showed that apoptosis of SH-SY5Y cells was induced by isatin. Furthermore, Bcl-2 expression was decreased and the ratio of Bcl-2 to Bax was significantly decreased by isatin. The mitochondrial transmembrane potential was markedly reduced and the release of cytochrome c into the cytosol was increased after treatment with isatin. Simultaneously, caspase-9, 3 was activated, followed by degradation of ICAD, a caspase-3 substrate. Finally, tumor xenograft growth was markedly suppressed and a decrease was found in Bcl-2 and Bax expression in vivo. These results suggest that isatin can induce apoptosis and inhibit the growth of neuroblastoma cells via the mitochondrial pathway.

The purpose of the study was to investigate the antitumor effects of Isatin and the related mechanism. Human neuroblastoma cells (SH-SY5Y) were exposed to Isatin at different concentrations for 48 h. Apoptotic features were demonstrated by means of nuclei staining with Hoechst 33258 and flow cytometry with Propidium Iodide (PI). Expressions of Bcl-2, Bax and Vascular endothelial growth factor (VEGF) mRNA were analyzed via RT-PCR. Expressions of Bcl-2, Bax proteins and phosphorylated extracellular signal regulated protein kinases (ERKs, p42/p44) were analyzed via Western blot. Activation of caspase-3 was assayed by flow cytometry with anti-active caspase-3-McAb-PE. VEGF protein was determined by ELISA kits. And the results showed that apoptosis of SH-SY5Y cells were induced by Isatin in a dose-dependent manner. Expressions of Bcl-2, VEGF mRNA and Bcl-2, VEGF proteins were down-regulated, while expressions of Bax mRNA and Bax protein were not changed obviously. Expression of phosphorylated ERKs decreased, but the level of activated caspase-3 increased after treatment of Isatin. These results suggest that Isatin promotes the apoptosis of neuroblastoma cells, therefore, it might be a potential candidate for the treatment of neuroblastoma.

Isatin is an endogenous indole in mammalian tissues and fluids that is expected to have antitumor effects in human breast cancer cells. Human breast cancer cells (MCF-7) were exposed to isatin at various concentrations (0, 50, 100, 200 µmol/l) for 48 h. Apoptotic features were demonstrated by nuclei staining with Hoechst 33258 and flow cytometry. Bcl-2 and Bax mRNA were analyzed via reverse transcription-polymerase chain reaction. Bcl-2, Bax, the inhibitor of caspase-activated DNase (ICAD), and cytochrome c protein were analyzed by western blot analysis. Apoptosis, caspase-9 and -3 activation and mitochondrial depolarization were assayed by flow cytometry. The results showed that isatin induced apoptosis of MCF-7 cells. Furthermore, Bcl-2 expression was decreased and the ratio of Bcl-2 to Bax was significantly decreased by isatin. The mitochondrial transmembrane potential was markedly decreased and the release of cytochrome c into the cytosol was elevated following treatment with isatin. At the same time, caspase-9 and -3 were stimulated, followed by the degradation of ICAD, a caspase-3 substrate.