BACKGROUND: Calpains are implicated in a wide range of cellular functions including the maintenance of hemostasis via the regulation of cytoskeletal modifications in platelets. OBJECTIVES: Determine the functional role of calpain isoforms in platelet spreading. METHODS AND RESULTS: Platelets from calpain-1(-/-) mice show enhanced spreading on collagen- and fibrinogen-coated surfaces as revealed by immunofluorescence, differential interference contrast (DIC) and scanning electron microscopy. The treatment of mouse platelets with MDL, a cell permeable inhibitor of calpains 1/2, resulted in increased spreading. The PTP1B-mediated enhanced tyrosine dephosphorylation in calpain-1(-/-) platelets did not fully account for the enhanced spreading as platelets from the double knockout mice lacking calpain-1 and PTP1B showed only a partial rescue of the spreading phenotype. In non-adherent platelets, proteolysis and GTPase activity of RhoA and Rac1 were indistinguishable between the wild-type (WT) and calpain-1(-/-) platelets. In contrast, the ECM-adherent calpain-1(-/-) platelets showed higher Rac1 activity at the beginning of spreading, whereas RhoA was more active at later time points. The ECM-adherent calpain-1(-/-) platelets showed an elevated level of RhoA protein but not Rac1 and Cdc42. Proteolysis of recombinant RhoA, but not Rac1 and Cdc42, indicates that RhoA is a calpain-1 substrate in vitro. CONCLUSIONS: Potentiation of the platelet spreading phenotype in calpain-1(-/-) mice suggests a novel role of calpain-1 in hemostasis, and may explain the normal bleeding time observed in the calpain-1(-/-) mice.
BACKGROUND: Calpains are implicated in a wide range of cellular functions including the maintenance of hemostasis via the regulation of cytoskeletal modifications in platelets. OBJECTIVES: Determine the functional role of calpain isoforms in platelet spreading. METHODS AND RESULTS: Platelets from calpain-1(-/-) mice show enhanced spreading on collagen- and fibrinogen-coated surfaces as revealed by immunofluorescence, differential interference contrast (DIC) and scanning electron microscopy. The treatment of mouse platelets with MDL, a cell permeable inhibitor of calpains 1/2, resulted in increased spreading. The PTP1B-mediated enhanced tyrosine dephosphorylation in calpain-1(-/-) platelets did not fully account for the enhanced spreading as platelets from the double knockout mice lacking calpain-1 and PTP1B showed only a partial rescue of the spreading phenotype. In non-adherent platelets, proteolysis and GTPase activity of RhoA and Rac1 were indistinguishable between the wild-type (WT) and calpain-1(-/-) platelets. In contrast, the ECM-adherent calpain-1(-/-) platelets showed higher Rac1 activity at the beginning of spreading, whereas RhoA was more active at later time points. The ECM-adherent calpain-1(-/-) platelets showed an elevated level of RhoA protein but not Rac1 and Cdc42. Proteolysis of recombinant RhoA, but not Rac1 and Cdc42, indicates that RhoA is a calpain-1 substrate in vitro. CONCLUSIONS: Potentiation of the platelet spreading phenotype in calpain-1(-/-) mice suggests a novel role of calpain-1 in hemostasis, and may explain the normal bleeding time observed in the calpain-1(-/-) mice.
Authors: A Huttenlocher; S P Palecek; Q Lu; W Zhang; R L Mellgren; D A Lauffenburger; M H Ginsberg; A F Horwitz Journal: J Biol Chem Date: 1997-12-26 Impact factor: 5.157
Authors: D A Potter; J S Tirnauer; R Janssen; D E Croall; C N Hughes; K A Fiacco; J W Mier; M Maki; I M Herman Journal: J Cell Biol Date: 1998-05-04 Impact factor: 10.539
Authors: Yongzhong Zhao; Nikolay L Malinin; Julia Meller; Yi Ma; Xiaoxia Z West; Kamila Bledzka; Jun Qin; Eugene A Podrez; Tatiana V Byzova Journal: J Biol Chem Date: 2012-09-25 Impact factor: 5.157
Authors: Jennifer O Nwankwo; Thomas Gremmel; Anja J Gerrits; Farha J Mithila; Rod R Warburton; Nicholas S Hill; Yunzhe Lu; Lauren J Richey; Joseph A Jakubowski; Andrew L Frelinger; Athar H Chishti Journal: Thromb Res Date: 2017-10-26 Impact factor: 3.944
Authors: Nadine J A Mattheij; Karen Gilio; Roger van Kruchten; Shawn M Jobe; Adam J Wieschhaus; Athar H Chishti; Peter Collins; Johan W M Heemskerk; Judith M E M Cosemans Journal: J Biol Chem Date: 2013-03-21 Impact factor: 5.157
Authors: Vanessa M Machado; Maria I Morte; Bruno P Carreira; Maria M Azevedo; Jiro Takano; Nobuhisa Iwata; Takaomi C Saido; Hannelore Asmussen; Alan R Horwitz; Caetana M Carvalho; Inês M Araújo Journal: Front Cell Neurosci Date: 2015-02-04 Impact factor: 5.505