pp60c-src associates with the SH2-containing inositol-5-phosphatase SHIP1 and is involved in its tyrosine phosphorylation downstream of alphaIIbbeta3 integrin in human platelets.
SH2-containing inositol-5-phosphatase 1 (SHIP1) was originally identified as a 145 kDa protein that became tyrosine-phosphorylated in response to multiple cytokines. It is now well established that SHIP1 is specifically expressed in haemopoietic cells and is important as a negative regulator of signalling. We found recently that SHIP1 was present in human blood platelets as an Ins(1,3,4, 5)P(4)-phosphatase and a PtdIns(3,4,5)P(3)-5-phosphatase that became tyrosine-phosphorylated and was relocated to the cytoskeleton in an integrin-dependent manner. Here we report biochemical and pharmacological evidence that the tyrosine kinase pp60(c-src) is constitutively associated with SHIP1 and is involved in its tyrosine phosphorylation downstream of integrin engagement in thrombin-activated human platelets. The use of cytochalasin D allowed us to demonstrate that the actin cytoskeleton reorganization induced on thrombin stimulation was not required for its integrin-mediated phosphorylation. Moreover, the integrin-dependent relocation of SHIP1 to the cytoskeleton did not require its tyrosine phosphorylation. These results suggest that SHIP1 is first recruited to the integrin-linked signalling complexes and then becomes tyrosine-phosphorylated through a Src-kinase-dependent mechanism but independently of the actin cytoskeleton reorganization.
Giuriato
S
S
Institut National de la Santé et de la Recherche Médicale, Unité 326, IFR30, Hôpital Purpan, 31059 Toulouse Cedex, France.
Bodin
S
S
Erneux
C
C
Woscholski
R
R
Plantavid
M
M
Chap
H
H
Payrastre
B
B
D000199:Actins / Q000378:metabolism; D001692:Biological Transport; D001792:Blood Platelets / Q000378:metabolism*; D003599:Cytoskeleton; D006801:Humans; D066298:In Vitro Techniques; D000072183:Phosphatidylinositol-3,4,5-Trisphosphate 5-Phosphatases; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000378:metabolism*; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013917:Thrombin / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism; D018909:src Homology Domains / Q000502:physiology*
D000199:Actins; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D014443:Tyrosine; D016392:Proto-Oncogene Proteins pp60(c-src); D010744:Phosphoric Monoester Hydrolases; C098706:INPPL1 protein, human; D000072183:Phosphatidylinositol-3,4,5-Trisphosphate 5-Phosphatases; D013917:Thrombin