Aims/hypothesis: Pancreatic AR42J cells express both exocrine and neuroendocrine properties. When exposed to activin A, approximately 50 % of the cells die within 3 days by apoptosis. Addition of hepatocyte growth factor prevents apoptosis induced by activin A and induces differentiation into insulin-producing cells. The present study was conducted to examine the role of mitogen-activated protein kinase and phosphoinositide 3-kinase in the action of hepatocyte growth factor.
Methods: The role of mitogen-activated protein kinase was assessed by using 2-(2'-amino-3 '-methoxyphenol)-oxanaphthalen-4-one (PD098059). Cells were also transfected with cDNA for mitogen-activated protein kinase phosphatase and constitutively active mutant of mitogen-activated protein kinase kinase.
Results: Hepatocyte growth factor induced sustained activation of the mitogen-activated protein kinase, which was inhibited by PD098059. PD098059 completely blocked the differentiation and also blocked the prevention of apoptosis. Transfection of the cells with cDNA for mitogen-activated protein kinase phosphatase reproduced the effect of PD098059. Conversely, transfection with cDNA for the constitutively active mutant of mitogen-activated protein kinase kinase reproduced the effect of hepatocyte growth factor. In contrast, addition of wortmannin or transfection of the dominantly negative form of the p85 subunit of the phosphoinositide 3-kinase did not affect differentiation induced by hepatocyte growth factor. Instead, wortmannin enhanced the increase in the insulin content of the differentiated AR42J cells.
Conclusion/interpretation: The MAP kinase pathway is necessary and sufficient for the action of HGF on differentiation of AR42J cells.