An as yet single family with a bleeding history is shown to present the characteristic lack of membrane expression of procoagulant phospholipids observed in Scott syndrome. Low prothrombin consumption in the serum of the propositus, a 71-year-old woman, and two of her children was the sole abnormal hemostasis parameter. The degree of exposure of procoagulant phospholipids, chiefly phosphatidylserine, was reduced in stimulated platelets, erythrocytes and Epstein-Barr virus- infected B lymphocytes. The data are compatible with homozygous status of the propositus and heterozygous status of her children. Scott syndrome appears to be transmitted as an autosomal recessive trait reflecting the deletion or mutation of a putative outward phosphatidylserine translocase. The detailed knowledge of this transporter could have an impact in membrane physiology.
Objective—
The gap junction protein connexin37 (Cx37) plays an important role in cell-cell communication in the vasculature. A C1019T Cx37 gene polymorphism, encoding a P319S substitution in the regulatory C terminus of Cx37 (Cx37CT), correlates with arterial stenosis and myocardial infarction in humans. This study was designed to identify potential binding partners for Cx37CT and to determine whether the polymorphism modified this interaction.
Methods and Results—
Using a high-throughput phage display, we retrieved 2 binding motifs for Cx37CT: WHK … [K,R]XP … and FHK … [K,R]XXP … , the first being more common for Cx37CT-319P and the second more common for Cx37CT-319S. One of the peptides (WHRTPRLPPPVP) showed 77.7% homology with residues 843 to 854 of endothelial nitric oxide synthase (eNOS). In vitro binding of this peptide or of the homologous eNOS sequence to both Cx37CT isoforms was confirmed by cross-linking and surface plasmon resonance. Electrophysiological analysis of Cx37 single channel activity in transfected N2a cells showed that eNOS-like and eNOS(843–854) increased the frequency of events with conductances higher than 300 pS. We demonstrated that eNOS coimmunoprecipitated with Cx37 in a mouse endothelial cell (EC) line (bEnd.3), human primary ECs, and a human EC line transfected with Cx37-319P or Cx37-319S. Cx37 and eNOS colocalized at EC membranes. Moreover, a dose-dependent increase in nitric oxide production was observed in ECs treated with Cx37 antisense.
Conclusion—
Overall, our data show for the first time a functional and specific interaction between eNOS and Cx37. This interaction may be relevant for the control of vascular physiology both in health and in disease.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.