Abstract
Somatostatin is involved in the regulation of multiple signaling pathways and affords neuroprotection in response to neurotoxins. In the present study, we investigated the role of Somatostatin-14 (SST) in cell viability and the regulation of phosphorylation of Collapsin Response Mediator Protein 2 (CRMP2) (Ser522) via the blockade of Ca2+ accumulation, along with the inhibition of cyclin-dependent kinase 5 (CDK5) and Calpain activation in differentiated SH-SY5Y cells. Cell Viability and Caspase 3/7 assays suggest that the presence of SST ameliorates mitochondrial stability and cell survival pathways while augmenting pro-apoptotic pathways activated by Aβ. SST inhibits the phosphorylation of CRMP2 at Ser522 site, which is primarily activated by CDK5. Furthermore, SST effectively regulates Ca2+ influx in the presence of Aβ, directly affecting the activity of calpain in differentiated SH-SY5Y cells. We also demonstrated that SSTR2 mediates the protective effects of SST. In conclusion, our results highlight the regulatory role of SST in intracellular Ca2+ homeostasis. The neuroprotective role of SST via axonal regeneration and synaptic integrity is corroborated by regulating changes in CRMP2; however, SST-mediated changes in the blockade of Ca2+ influx, calpain expression, and toxicity did not correlate with CDK5 expression and p35/25 accumulation. To summarize, our findings suggest two independent mechanisms by which SST mediates neuroprotection and confirms the therapeutic implications of SST in AD as well as in other neurodegenerative diseases where the effective regulation of calcium homeostasis is required for a better prognosis.
Highlights
Alzheimer’s disease (AD) is a progressive neurodegenerative disorder and the most common form of dementia in the elderly population
We have previously demonstrated the effect of SST in promoting the retinoic acid (RA)-induced differentiation of SH-SY5Y
We recently demonstrated that Somatostatin-14 (SST) mediates the promotion of the overall neurite length in RA-differentiated SH-SY5Y cells, with specific effects on microtubule-associated proteins such as MAP2 and Tau [40]
Summary
Alzheimer’s disease (AD) is a progressive neurodegenerative disorder and the most common form of dementia in the elderly population. The overaccumulation of Aβ is considered as the prominent cause of disease severity and neuronal cell death; the precise mechanism of interconnecting AD onset and progression is not fully understood, despite the identification of signaling pathways that exert determinant roles [8,9]. One such crucial signaling molecule that may represent a critical determinant is collapse response mediator
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