| Budget Amount *help |
¥5,460,000 (Direct Cost: ¥4,200,000、Indirect Cost: ¥1,260,000)
Fiscal Year 2014: ¥1,430,000 (Direct Cost: ¥1,100,000、Indirect Cost: ¥330,000)
Fiscal Year 2013: ¥1,950,000 (Direct Cost: ¥1,500,000、Indirect Cost: ¥450,000)
Fiscal Year 2012: ¥2,080,000 (Direct Cost: ¥1,600,000、Indirect Cost: ¥480,000)
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| Outline of Final Research Achievements |
We examined the role of SPHKAP in glucose- and exendin-4-stimulated insulin secretion. Quantitative real-time PCR and western blot showed that SPHKAP was highly expressed in beta-cells. Immunoprecipitation showed that SPHKAP interacted with PKA-RI subunit but not with PKA-RII subunit in SPHKAP-overexpressed HEK293 and INS-1D cells. Immunohistochemical staining revealed that SPHKAP was localized in beta-cells and not in alpha-cells of islets from Wistar rats, C57BL/6 mice and human. Confocal microscopy and electron microscopy analysis clarified that SPHKAP was co-localized with insulin secretory granules. Overexpression of SPHKAP decreased glucose-stimulated insulin secretion by about 50% and exendin-4-stimulated insulin secretion by about 35%. Knock down of endogenous SPHKAP resulted in about 1.5-fold increase in glucose- and exendin-4-stimulated insulin secretion. These results demonstrate that SPHKAP is localized on insulin secretory granules, and inhibits insulin secretion.
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