Structural, functional, and mechanistic insights uncover the fundamental role of orphan connexin-62 in platelets

Connexins oligomerise to form hexameric hemichannels in the plasma membrane that can further dock together on adjacent cells to form gap junctions and facilitate intercellular trafficking of molecules. In this study, we report the expression and function of an orphan connexin, connexin-62 (Cx62), in human and mouse (Cx57, mouse homolog) platelets. A novel mimetic peptide ((62)Gap27) was developed to target the second extracellular loop of Cx62, and 3-dimensional structural models predicted its interference with gap junction and hemichannel function. The ability of (62)Gap27 to regulate both gap junction and hemichannel-mediated intercellular communication was observed using fluorescence recovery after photobleaching analysis and flow cytometry. Cx62 inhibition by (62)Gap27 suppressed a range of agonist-stimulated platelet functions and impaired thrombosis and hemostasis. This was associated with elevated protein kinase A-dependent signaling in a cyclic adenosine monophosphate-independent manner and was not observed in Cx57-deficient mouse platelets (in which the selectivity of (62)Gap27 for this connexin was also confirmed). Notably, Cx62 hemichannels were observed to function independently of Cx37 and Cx40 hemichannels. Together, our data reveal a fundamental role for a hitherto uncharacterized connexin in regulating the function of circulating cells.

Automated summary

Connexins form hexameric hemichannels in the plasma membrane, which can dock together to form gap junctions and facilitate intercellular trafficking of molecules. A study on the orphan connexin Cx62 in human and mouse platelets revealed the development of a novel mimetic peptide ((62)Gap27) to interfere with its function and its impact on platelet functions. The inhibition of Cx62 by (62)Gap27 suppressed platelet functions and impaired thrombosis, showing a fundamental role of Cx62 in regulating circulating cell functions.