Insulin promotes neuronal survival via the alternatively spliced protein kinase CδII isoform.

Abstract

Insulin signaling pathways in the brain regulate food uptake and memory and learning. Insulin and protein kinase C (PKC) pathways are integrated and function closely together. PKC activation in the brain is essential for learning and neuronal repair. Intranasal delivery of insulin to the central nervous system (CNS) has been shown to improve memory, reduce cerebral atrophy, and reverse neurodegeneration. However, the neuronal molecular mechanisms of these effects have not been studied in depth. PKCδ plays a central role in cell survival. Its splice variants, PKCδI and PKCδII, are switches that determine cell survival and fate. PKCδI promotes apoptosis, whereas PKCδII promotes survival. Here, we demonstrate that insulin promotes alternative splicing of PKCδII isoform in HT22 cells. The expression of PKCδI splice variant remains unchanged. Insulin increases PKCδII alternative splicing via the PI3K pathway. We further demonstrate that Akt kinase mediates phosphorylation of the splicing factor SC35 to promote PKCδII alternative splicing. Using overexpression and knockdown assays, we demonstrate that insulin increases expression of Bcl2 and bcl-xL via PKCδII. We demonstrate increased cell proliferation and increased BrdU incorporation in insulin-treated cells as well as in HT22 cells overexpressing PKCδII. Finally, we demonstrate in vivo that intranasal insulin promotes cognitive function in mice with concomitant increases in PKCδII expression in the hippocampus. This is the first report of insulin, generally considered a growth or metabolic hormone, regulating the alternative isoform expression of a key signaling kinase in neuronal cells such that it results in increased neuronal survival.

• Authors: André Apostolatos, Shijie Song, Sandra Acosta, Mishka Peart, James E Watson, Paula Bickford, Denise R Cooper, Niketa A Patel
• Journal: The Journal of biological chemistry (J Biol Chem) Vol. 287 Issue 12 Pg. 9299-310 (Mar 16 2012) ISSN: 1083-351X [Electronic] United States
• PMID: 22275369 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, Non-P.H.S.)

Chemical References

• Insulin
• Proto-Oncogene Proteins
• Proto-Oncogene Proteins c-bcl-2
• bcl-X Protein
• Bcl2 protein, mouse
• Protein Kinase C-delta

Topics

• Alternative Splicing
• Animals
• Cell Line
• Cell Survival
• Gene Expression Regulation
• Insulin (metabolism)
• Male
• Mice
• Mice, Inbred C57BL
• Neurons (cytology, enzymology, metabolism)
• Protein Kinase C-delta (genetics, metabolism)
• Proto-Oncogene Proteins (genetics, metabolism)
• Proto-Oncogene Proteins c-bcl-2
• Signal Transduction
• bcl-X Protein (genetics, metabolism)