title: RhoA/ROCK signaling contributes to sex differences in the activation of human platelets.
abstract: Studies of sex-dependent differences in platelet aggregation and glycoprotein (GP)IIb/IIIa activation have demonstrated that platelets from females are more sensitive to agonists than those from males. To date, there is little understanding of these differences at a molecular level. Here, sex differences in reactivity of platelets from 86 women and 86 men were investigated. Platelet degranulation (CD62P expression) and activation of GPIIb/IIIa (PAC-1 binding), with and without ADP, were assessed. Extent of shape change (ESC) in response to ADP was measured. Basal CD62P and PAC-1 expression did not differ between the sexes. In response to ADP activation, mean PAC-1 binding in platelets from female donors was 17.9±3.5% vs. 14.0±4.1% in platelets from male donors, and ESC was significantly greater in platelets from females (p<0.05). Evaluation of basal expression of signaling molecules along the ADP receptor pathway leading to GPIIb/IIIa activation and subsequent RhoA/ROCK signaling via GPIIb/IIIa 'outside-in' signaling showed that platelets from females produce 3-fold greater levels of phosphorylated protein kinase C (PKC) substrates. There was a 2.5-fold greater level of activated RhoA, and platelet sub-fractionation analysis demonstrated 2.7-fold more RhoA in the membrane fraction of female vs. male platelets. Similarly, there was a 2.8-fold increase in levels of phosphorylated myosin light chain (MLC) in platelets from females vs. males. The increased signaling activity in platelets from females mirrors their greater sensitivity to agonists. These findings further our understanding of the molecular differences between platelets from males and females.
authors.affiliation: Centre for Innovation, Canadian Blood Services, Vancouver, BC, Canada; Centre for Blood Research, University of British Columbia, Vancouver, BC, Canada; Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Peter
authors.initials: P
authors.lastname: Schubert
authors.affiliation: Centre for Innovation, Canadian Blood Services, Vancouver, BC, Canada; Centre for Blood Research, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Danielle
authors.initials: D
authors.lastname: Coupland
authors.affiliation: Centre for Blood Research, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Marie
authors.initials: M
authors.lastname: Nombalais
authors.affiliation: Centre for Innovation, Canadian Blood Services, Vancouver, BC, Canada; Centre for Blood Research, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Geraldine
authors.initials: G
authors.lastname: M Walsh
authors.affiliation: Centre for Innovation, Canadian Blood Services, Vancouver, BC, Canada; Centre for Blood Research, University of British Columbia, Vancouver, BC, Canada; Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, BC, Canada. Electronic address: dana.devine@blood.ca.
authors.forename: Dana V
authors.initials: DV
authors.lastname: Devine
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001792:Blood Platelets / Q000166:cytology* / Q000378:metabolism; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D019007:P-Selectin / Q000378:metabolism; D010766:Phosphorylation; D010974:Platelet Aggregation; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism; D012727:Sex Characteristics; D015398:Signal Transduction; D055815:Young Adult; D054460:rho-Associated Kinases / Q000378:metabolism*; D020742:rhoA GTP-Binding Protein / Q000378:metabolism*
chemical_list: D019007:P-Selectin; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; C546937:SELP protein, human; C066737:RHOA protein, human; D054460:rho-Associated Kinases; D011493:Protein Kinase C; D020742:rhoA GTP-Binding Protein
keywords: Blood; GTPase; Platelets; Sex differences; Signal transduction