RESUMO
This study examined circadian variation in coagulation and fibrinolytic parameters among Jcl:ICR, C3H/HeN, BALB/cA, and C57BL/6J strains of mice. Plasma plasminogen activator inhibitor 1 (PAI-1) levels fluctuated in a circadian manner and peaked in accordance with the mRNA levels at the start of the active phase in all strains. Fibrinogen mRNA levels peaked at the start of rest periods in all strains, although plasma fibrinogen levels remained constant. Strain differences in plasma antithrombin (AT) activity and protein C (PC) levels were then identified. Plasma AT activity was circadian rhythmic only in Jcl:ICR, but not in other strains, although the mRNA levels remained constant in all strains. Levels of plasma PC and its mRNA fluctuated in a circadian manner only in Jcl:ICR mice, whereas those of plasma prothrombin, factor X, factor VII, prothrombin time (PT), and activated partial thrombin time (APTT) remained constant in all strains. These results suggest that genetic heterogeneity underlies phenotypic variations in the circadian rhythmicity of blood coagulation and fibrinolysis. The circadian onset of thrombotic events might be due in part to the rhythmic gene expression of coagulation and fibrinolytic factors. The present study provides fundamental information about mouse strains that will help to understand the circadian variation in blood coagulation and fibrinolysis.
Assuntos
Coagulação Sanguínea/fisiologia , Ritmo Circadiano/genética , Fibrinólise/genética , Variação Genética , Animais , Testes de Coagulação Sanguínea/métodos , Ritmo Circadiano/fisiologia , Fator VII/genética , Fator X/genética , Fibrinogênio/análise , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C3H , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos ICR , Inibidor 1 de Ativador de Plasminogênio/sangue , Inibidor 1 de Ativador de Plasminogênio/genética , Proteína C/análise , RNA Mensageiro/metabolismo , Especificidade da EspécieRESUMO
BACKGROUND: Recent studies have revealed that aPKC (atypical protein kinase C), PAR-3 and PAR-6 play indispensable roles in the regulation of various cell polarization events, from worms to mammals, suggesting that they comprise an evolutionarily conserved protein machinery which is essential for cell polarization. The three proteins interact with each other to form a ternary complex and thus mutually regulate their functionality and localization. Here, we investigated the biochemical nature of the aPKC-PAR-3 interaction in detail to clarify its functional importance in cell polarity. RESULTS: The highly conserved 26 amino acid sequence 816-841, in PAR-3 was found to be necessary and sufficient for the tight association with aPKC. Among several conserved serine/threonine residues within the region, aPKC preferentially phosphorylates serine-827 in vitro, and this phosphorylation reduces the stability of the PAR-3-aPKC interaction. Several analyses using a phospho-serine 827 specific antibody have established that this phosphorylation by aPKC occurs in vivo. Over-expression of a point mutant of PAR-3 (S827A), which is predicted to form a stable complex with aPKC, causes defects in the cell-cell contact-induced cell polarization of epithelial MDCK cells, similarly to a dominant negative mutant of aPKC. CONCLUSIONS: These results imply that serine 827 in the aPKC binding site of PAR-3 is a target of aPKC and that the regulated interaction between a protein kinase, aPKC, and its substrate, PAR-3, plays an essential role in the establishment of cell polarity.