The human proteinase-activated receptor-3 (PAR-3) gene. Identification within a Par gene cluster and characterization in vascular endothelial cells and platelets.
Proteolytically activated receptors (PARs) represent an emerging subset of seven transmembrane G protein-coupled receptors that mediate cell activation events by receptor cleavage at distinct scissile bonds located within receptor amino termini. Differential genomic blotting using a yeast artificial chromosome known to contain the PAR-1 and PAR-2 genes identified the PAR-3 gene within a PAR gene cluster spanning approximately 100 kilobases at 5q13. The PAR-3 gene is relatively small (approximately 12 kilobases); and, like the PAR-1 and PAR-2 genes, it displays a two-exon structure, with the majority of the coding sequence and the proteolytic cleavage site contained within the larger second exon. Sequence analysis of the 5'-flanking region demonstrates that the promoter is TATA-less, similar to that seen with PAR-1, with the identification of nucleic acid motifs potentially involved in transcriptional gene regulation, including AP-1, GATA, and octameric sequences. PAR-3 transcripts were apparent in human vascular endothelial cells, although at considerably lower levels than those of PAR-1 and not significantly modulated by the endothelial cell stimulus tumor necrosis factor-alpha. Likewise, although PAR-3 mRNA was evident in human platelets, receptor cell surface expression was modest (approximately 10%) compared with that of PAR-1. Thus, although PAR-3 is postulated to represent a second thrombin receptor, its modest endothelial cell and platelet expression suggest that PAR-3 activation by alpha-thrombin is less relevant for physiological responses in these mature cells. Rather, given its disparately greater expression in megakaryocytes (and megakaryocyte-like human erythroleukemia cells), a regulatory role in cellular development (by protease activation) could be postulated.
Schmidt
V A
VA
Department of Medicine, State University of New York at Stony Brook, Stony Brook, New York 11794, USA.
Nierman
W C
WC
Maglott
D R
DR
Cupit
L D
LD
Moskowitz
K A
KA
Wainer
J A
JA
Bahou
W F
WF
D000595:Amino Acid Sequence; D001483:Base Sequence; D001792:Blood Platelets / Q000502:physiology; D002478:Cells, Cultured; D002874:Chromosome Mapping; D002895:Chromosomes, Human, Pair 5; D003001:Cloning, Molecular; D010450:Endopeptidases / Q000502:physiology; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D008565:Membrane Proteins / Q000502:physiology; D008969:Molecular Sequence Data; D009131:Muscle, Smooth, Vascular / Q000502:physiology; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism; D044464:Receptor, PAR-2; D011956:Receptors, Cell Surface / Q000235:genetics*; D018179:Receptors, Thrombin / Q000235:genetics* / Q000502:physiology; D017422:Sequence Analysis, DNA
D008565:Membrane Proteins; D012333:RNA, Messenger; D044464:Receptor, PAR-2; D011956:Receptors, Cell Surface; D018179:Receptors, Thrombin; C105295:protease-activated receptor 3; D010450:Endopeptidases; D019204:GTP-Binding Proteins