sst2 somatostatin receptor mediates negative regulation of insulin receptor signaling through the tyrosine phosphatase SHP-1.
We have previously reported in Chinese hamster ovary (CHO) cells expressing sst2 that activation of the sst2 somatostatin receptor inhibits insulin-induced cell proliferation by a mechanism involving stimulation of a tyrosine phosphatase activity. Here we show that the tyrosine phosphatase SHP-1 was associated with the insulin receptor (IR) at the basal level. Activation of IR by insulin resulted in a rapid and transient increase of tyrosine phosphorylation of IR, its substrates IRS-1 and Shc, and also of SHP-1. This was then followed by a rapid dephosphorylation of these molecules, which was related to the insulin-induced increase of SHP-1 association to IR and of SHP-1 activity. On the other hand, addition to insulin of the somatostatin analogue, RC160, resulted in a higher and faster increase of SHP-1 association to IR directly correlated with an inhibition of phosphorylation of IR and its substrates, IRS-1 and Shc. RC160 also induced a higher and more sustained increase in SHP-1 activity. Furthermore, RC160 completely suppressed the effect of insulin on SHP-1 phosphorylation. Finally, in CHO cells coexpressing sst2 and a catalytically inactive mutant SHP-1, insulin as well as RC160 could no longer stimulate SHP-1 activity. Overexpression of the SHP-1 mutant prevented the insulin-induced signaling to be terminated by dephosphorylation of IR, suppressed the inhibitory effect of RC160 on insulin-induced IR phosphorylation, and abolished the cell proliferation modulation by insulin and RC160. Our results suggest that SHP-1 plays a role in negatively modulating insulin signaling by association with IR. Furthermore, somatostatin inhibits the insulin-induced mitogenic signal by accelerating and amplifying the effect of SHP-1 on the termination of the insulin signaling pathway.
Bousquet
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C
INSERM U151, Institut Louis Bugnard, IFR 31, CHU Rangueil, 31403 Toulouse Cedex 04, France.
Delesque
N
N
Lopez
F
F
Saint-Laurent
N
N
Estève
J P
JP
Bedecs
K
K
Buscail
L
L
Vaysse
N
N
Susini
C
C
D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D047908:Intracellular Signaling Peptides and Proteins; D010766:Phosphorylation; D011485:Protein Binding; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism*; D011972:Receptor, Insulin / Q000378:metabolism*; D017481:Receptors, Somatostatin / Q000378:metabolism*; D015398:Signal Transduction; D014443:Tyrosine / Q000378:metabolism
D047908:Intracellular Signaling Peptides and Proteins; D017481:Receptors, Somatostatin; D014443:Tyrosine; D011972:Receptor, Insulin; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases