Insulin signaling: Tyrosine kinase activity in the crab Chasmagnathus granulata gills

Abstract

Insulin-specific binding sites were recently shown in the gills of the estuarine crab Chasmagnathus granulata. In order to study the insulin receptor in these gills, its tyrosine kinase activity was evaluated in crude membranes and in isolated insulin receptor. The tyrosine kinase activity was determined by the insulin receptor capacity to autophosphorylate and phosphorylate exogenous substrate poly (Glu:Tyr 4:1) in the presence of bovine insulin (10–7M). When stimulated with insulin the 95 kDa β-subunit was phosphorylated and identified by autoradiography. The insulin receptor stimulated with insulin showed an 1.3-fold increase of [γ32P]ATP incorporation to the exogenous substrate poly (Glu:Tyr 4:1). This increase was not observed when previously incubated with genistein. Further studies will be required to understand other steps of the insulin signaling chain in this organ. J. Exp. Zool. 283:91–94, 1999. © 1999 Wiley-Liss, Inc.