Role of mitogen-activated protein kinase and phosphoinositide 3-kinase in the differentiation of rat pancreatic AR42J cells induced by hepatocyte growth factor

Abstract

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. 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. 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. The MAP kinase pathway is necessary and sufficient for the action of HGF on differentiation of AR42J cells.