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Sorting nexin 19 regulates the number of dense core vesicles in pancreatic β-cells
Shin-Ichi Harashima1, Takahiko Horiuchi2, Yu Wang1
1Department of Diabetes and Clinical Nutrition, Graduate School of Medicine, Kyoto University, Kyoto.
Unlabelled:
Aims/Introduction: Insulinoma-associated protein 2 (IA-2) regulates insulin secretion and the number of dense core vesicles (DCV). However, the mechanism of regulation of DCV number by IA-2 is unknown. We examined the effect of sorting nexin 19 (SNX19), an IA-2 interacting protein, on insulin secretion and the number of dense core vesicles (DCV).
Materials And Methods:
Stable SNX19 knockdown (SNX19KD) MIN6, a mouse pancreatic β-cell line, and stable SNX19-reintroduced SNX19KD MIN6 were established. Quantification of DCV, and lysosomes was carried out using electron micrographs. The half-life of DCV was detected by pulse-chase experiment.
Results:
Insulin secretion and content were decreased in stable SNX19KD MIN6 cells compared with those in control MIN6 cells. Electron micrographs showed that DCV number in SNX19KD cells was decreased by approximately 75% and that DCV size was decreased by approximately 40% compared with those in control cells, respectively. Furthermore, when SNX19 was reintroduced in SNX19KD cells, insulin content, insulin secretion and DCV number were increased. The half-life of DCV was decreased in SNX19KD cells, but was increased in SNX19KD cells in which SNX19 was reintroduced. The number of lysosomes and the activity of lysosome enzyme cathepsin D were increased by approximately threefold in SNX19KD cells compared with those in control cells. In contrast, they were decreased to approximately half to one-third in SNX19-reintroduced SNX19KD cells.
Conclusions:
SNX19 regulates the number of DCV and insulin content by stabilizing DCV in β-cells. (J Diabetes Invest, doi: 10.1111/j.2040-1124.2011.00138.x, 2012).
Insights
Sorting nexin 19 (SNX19) stabilizes dense core vesicles (DCV) in pancreatic beta cells, regulating insulin secretion and content. This finding clarifies the mechanism by which insulinoma-associated protein 2 (IA-2) influences insulin production.
Area of Science:
- Cell Biology
- Endocrinology
- Molecular Biology
Background:
- Insulinoma-associated protein 2 (IA-2) is known to regulate insulin secretion and dense core vesicle (DCV) numbers in pancreatic beta cells.
- The precise mechanism by which IA-2 controls DCV numbers remains largely unknown.
Purpose of the Study:
- To investigate the role of sorting nexin 19 (SNX19), a protein interacting with IA-2, in regulating insulin secretion and DCV numbers.
- To elucidate the mechanism of SNX19-mediated regulation of DCV stability and insulin content.
Main Methods:
- Stable SNX19 knockdown (SNX19KD) and SNX19-reintroduced MIN6 mouse pancreatic beta cell lines were generated.
- Quantification of DCV and lysosomes was performed using electron microscopy.
- DCV half-life was assessed via pulse-chase experiments, and lysosomal activity was measured.
Main Results:
- SNX19 knockdown significantly decreased insulin secretion, content, and DCV number (by ~75%) and size (by ~40%) in MIN6 cells.
- Reintroduction of SNX19 restored insulin levels, secretion, and DCV numbers.
- SNX19 knockdown increased lysosome numbers and cathepsin D activity, while decreasing DCV half-life; SNX19 reintroduction reversed these effects.
Conclusions:
- SNX19 plays a critical role in stabilizing DCVs within pancreatic beta cells.
- SNX19 regulates insulin content and secretion by modulating DCV stability, providing a key mechanistic insight into IA-2 function.