The tyrosine phosphatase CD148 is an essential positive regulator of platelet activation and thrombosis

Abstract

Platelets play a fundamental role in hemostasis and thrombosis. They are also involved in pathologic conditions resulting from blocked blood vessels, including myocardial infarction and ischemic stroke. Platelet adhesion, activation, and aggregation at sites of vascular injury are regulated by a diverse repertoire of tyrosine kinase–linked and G protein–coupled receptors. Src family kinases (SFKs) play a central role in initiating and propagating signaling from several platelet surface receptors; however, the underlying mechanism of how SFK activity is regulated in platelets remains unclear. CD148 is the only receptor-like protein tyrosine phosphatase identified in platelets to date. In the present study, we show that mutant mice lacking CD148 exhibited a bleeding tendency and defective arterial thrombosis. Basal SFK activity was found to be markedly reduced in CD148-deficient platelets, resulting in a global hyporesponsiveness to agonists that signal through SFKs, including collagen and fibrinogen. G protein–coupled receptor responses to thrombin and other agonists were also marginally reduced. These results highlight CD148 as a global regulator of platelet activation and a novel antithrombotic drug target.

Tetraspanin Tspan9 regulates platelet collagen receptor GPVI lateral diffusion and activation

“…Lumi-aggregometry was conducted as previously described [34]. For the platelet flow adhesion assay, flow cells in a 24-well plate format (Fluxion) were coated with 30 µg/mL collagen for one hour and blocked with 5 mg/mL of denatured, filtered fatty acid-free bovine serum albumin at 4 °C overnight.…”

“…Bleeding time was assessed in the mice using a previously described tail bleeding assay [34]. Intravital assessment of in vivo thrombus formation, after topical application of FeCl 3 to mesenteric or carotid arteries, was done as previously described [35].…”

Regulation of Src Family Kinases Involved in T Cell Receptor Signaling by Protein-tyrosine Phosphatase CD148

“…CD148 has been previously shown to play a positive role in surface receptor signal transduction via dephosphorylation of inhibitory tyrosines of SFKs in B cells, macrophages, platelets, and some non-hematopoietic tissues (19,(23)(24)(25). On the other hand, CD148 has been reported to act as a negative regulator of signal transduction in many non-hematopoietic biological systems as well as in TCR signaling in human T cell line Jurkat (29 -31).…”

“…Double-deficient cells were unable to signal via B cell receptor and FcR due to the inactivation of SFKs, which were hyperphosphorylated at their inhibitory tyrosines (24). In platelets, which do not express CD45, CD148 inactivation alone was sufficient to block signaling through glycoprotein VI and ␣IIb␤3 integrin, again most likely due to the inability of CD148-deficient platelets to activate SFKs (25).…”

Grape Seed Extracts Inhibit Platelet Aggregation by Inhibiting Protein Tyrosine Phosphatase

“…Recently, the receptor-like PTP CD148 has been reported to positively regulate the downstream activation of signals of both tyrosine kinaselinked receptor and GPCR. 20 It is possible that MBA and CS also inhibit CD148 activity. Consistent with this notion, we showed that PTP inhibitor-II, a chemical inhibitor that mainly acts on SHP-1 and other tyrosine phosphatases, inhibits collagen-and TRAP-induced platelet aggregation ( Figure 2C) and increases basal levels of tyrosine phosphorylation ( Figure 2B).…”