PROTEINASE-ACTIVATED RECEPTOR-2 - EXPRESSION BY HUMAN NEUTROPHILS

Neutrophils were shown to express the proteinase-activated receptor-2 (PAR-2), a seven transmembrane domain receptor, which is activated by cleavage by trypsin, Granulocytes from 14 donors stained positively fo r PAR-2 with affinity-purified rabbit antibodies raised against a pept ide corresponding to the trypsin cleavage site of human PAR-2, Neutrop hil activation in response to a receptor activating peptide (RAP) vari ed between donors. RAP (Ser-Leu-Ile-Gly-Lys-Val-NH2) alone induced an increase in the forward and side light scatter after 5-10 minutes and a small increase in the expression of the activation molecule CD11b. T he increased expression of CD11b induced by RAP was markedly enhanced by priming the neutrophils with a low concentration (1 nM) of formyl-L eu-Met-Phe. Trypsin and RAP also induced an increase in intracellular calcium, but there were large variations in the magnitude of responses between donors also in this assay. The effects of RAP in the differen t assays were specific; acetylated RAP was completely without activity .