IGF-1R/YAP signaling pathway is involved in collagen V-induced insulin biosynthesis and secretion in rat islet INS-1 cells.

PURPOSE: Type V collagen (collagen V) is one of the important components of extracellular matrix (ECM) in pancreas. We previously reported that pre-coating collagen V on the culture dishes enhanced insulin production in INS-1 rat pancreatic ß cells. In this study, we investigate the underlying mechanism. RESULTS: Insulin biosynthesis and secretion are both increased in INS-1 cells cultured on collagen V-coated dishes, accompanied by the reduced nuclear translocation of Yes-associated protein (YAP), a transcriptional co-activator. YAP, the downstream effector of Hippo signaling pathway, plays an important role in the development and function of pancreas. Inhibition of YAP activation by verteporfin further up-regulates insulin biosynthesis and secretion. Silencing large tumor suppressor (LATS), a core component of Hippo pathway which inhibits activity of YAP by phosphorylation, by siRNA transfection inhibits both insulin biosynthesis and secretion. In the present study, the protein level of insulin-like growth factor 1 receptor (IGF-1 R), detected as the upstream molecule of YAP, is reduced in the INS-1 cells cultured on the dishes coated with collagen V. The silencing of IGF-1 R by siRNA transfection further enhances insulin biosynthesis and secretion. IGF-1 treatment reduces collagen V-induced up-regulation of insulin biosynthesis and secretion, accompanying the increased nuclear YAP. CONCLUSION: Inhibition of IGF-1 R/YAP signal pathway is involved in collagen V-induced insulin biosynthesis and secretion in INS-1 cells.

Collagen type I enhances cell growth and insulin biosynthesis in rat pancreatic cells.

Type I collagen (collagen I) is the most abundant component of the extracellular matrix (ECM) in the pancreas. We previously reported that collagen I-coated culture dishes enhanced proliferation of rat pancreatic ß cell line, INS-1 cells, via up-regulation of ß-catenin nuclear translocation. In this study, we further investigated the effects of collagen I on insulin production of INS-1 cells. The results indicate that insulin synthesis as well as cell proliferation is increased in the INS-1 cells cultured on the dishes coated with collagen I. Up-regulation of insulin-like growth factor 1 receptor (IGF-1R) on the INS-1 cells cultured on the collagen-coated dishes is involved in up-regulation of cell proliferation and increase of insulin biosynthesis; however, up-regulation of insulin secretion in the INS-1 cells on collagen I-coated dishes was further enhanced by inhibition of IGF-1R. Autophagy of INS-1 cells on collagen I-coated dishes was repressed via IGF-1R upregulation, and inhibition of autophagy with 3MA further enhanced cell proliferation and insulin biosynthesis but did not affect insulin secretion. E-cadherin/ß-catenin adherent junction complexes are stabilized by autophagy. That is, autophagy negatively regulates the nuclear translocation of ß-catenin that leads to insulin biosynthesis and cell proliferation. In conclusion, IGF-1R/downregulation of autophagy/nuclear translocation of ß-catenin is involved in collagen I-induced INS-1 cell proliferation and insulin synthesis.

Collagens I and V differently regulate the proliferation and adhesion of rat islet INS-1 cells through the integrin ß1/E-cadherin/ß-catenin pathway.

Extracellular matrix (ECM) plays an important role in tissue repair, cell proliferation, and differentiation. Our previous study showed that collagen I and collagen V differently regulate the proliferation of rat pancreatic ß cells (INS-1 cells) through opposite influences on the nuclear translocation of ß-catenin. In this study, we investigated the ß-catenin pathway in INS-1 cells on dishes coated with collagen I or V. We found that nuclear translocation of the transcription factor Yes-associated protein (YAP) was enhanced by collagen I and suppressed by collagen V, but had no effect on INS-1 cell proliferation. Morphologically, INS-1 cells on collagen V-coated dishes showed stronger cell-to-cell adhesion, while the cells on collagen I-coated dishes showed weaker cell-to-cell adhesion in comparison with the cells on non-coated dishes. E-cadherin played an inhibitory role in the proliferation of INS-1 cells cultured on collagen I or collagen V coated dishes via regulation of the nuclear translocation of ß-catenin. Integrin ß1 was enhanced with collagen I, while it was repressed with collagen V. The integrin ß1 pathway positively regulated the cell proliferation. Inhibition of integrin ß1 pathway restored the protein level of E-cadherin and inhibited the nuclear translocation of ß-catenin in the cells on collagen I-coated dishes, but no effect was observed in the cells on collagen V-coated dishes. In conclusion, collagen I enhances the proliferation of INS-1 cells via the integrin ß1 and E-cadherin/ß-catenin signaling pathway. In INS-1 cells on collagen V-coated dishes, both integrin ß1 and E-cadherin/ß-catenin signal pathways are involved in the inhibition of proliferation.