INSULIN INDUCES TYROSINE DEPHOSPHORYLATION OF A 92 KDA PROTEIN IN SUSPENDED MONOCYTES

Monocytes bear insulin receptors similar to those expressed in other t issues, but insulin action in these cells remains unclear. There is ev idence that adhesion, by generating a complex array of irreversible tr ansformations, may modify the response of cells to other stimuli, such as hormones. The present study aimed to characterise the pattern of i nsulin induced tyrosine phosphorylation of monocytes in suspension. Mo nocytes in suspension were obtained by sequential gradient centrifugat ion and the tyrosine phosphoproteins were analyzed by immunoblot with antiphosphotyrosine antibodies. The major result of the study is that in suspended monocytes insulin induced a dose and time dependent depho sphorylation of a protein with a molecular mass of about 92 kDa withou t stimulating the tyrosine phosphorylation of the Insulin Receptor Sub strat-1 (IRS-1). In conclusion, we showed that in monocytes in suspens ion insulin seems to activate a tyrosine phosphatase, which, in turn, dephosphorylates a protein with an apparent molecular weight of 92 kDa . (C) 1998, Editrice Kurtis.