The response to thrombin of human neutrophils: evidence for two novel receptors.
Human alpha-thrombin was a chemoattractant for human neutrophils yielding a maximal response of similar magnitude to that observed with formyl-Met-Leu-Phe. The observed chemotaxis was not due to stimulation of the proteolytically activated thrombin receptor since: (1) this receptor was not detected by flow cytometry; (2) the inactive thrombin mutant Ser195-->Ala elicited a chemotactic response indistinguishable from that caused by wild-type thrombin; (3) antibodies to the cleavage site of the proteolytically activated receptor did not affect thrombin-induced chemotaxis; (4) a thrombin receptor activating peptide (TRAP) failed to stimulate chemotaxis. These data indicate the existence of a thrombin receptor for neutrophil chemotaxis which is not activated by proteolysis. In addition, although wild-type and ser195-->Ala thrombin did not cause an increase in intracellular Ca2+, a Ca2+ response to TRAP was observed with neutrophils from some donors. The TRAP-induced increase in Ca2+ was reproducible, dose dependent and specific. The use of alanine-substituted peptides demonstrated that the Ca2+ response was due to TRAP stimulation of a receptor other than the proteolytically activated thrombin receptor. Thus, it is necessary to re-evaluate the assumption made in previous studies that responses to TRAP are mediated by the proteolytically activated thrombin receptor.
Department of Haematology, University of Cambridge, UK.
A L
AL
Jenkins
G L
GL
Howells
E
E
Scott
B F
BF
Le Bonniec
M A
MA
Curtis
S R
SR
Stone
D000328:Adult; D000595:Amino Acid Sequence; D002118:Calcium / Q000097:blood; D002634:Chemotaxis, Leukocyte / Q000187:drug effects*; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation; D009504:Neutrophils / Q000187:drug effects* / Q000378:metabolism; D010446:Peptide Fragments / Q000378:metabolism; D018179:Receptors, Thrombin / Q000187:drug effects* / Q000378:metabolism; D013917:Thrombin / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*
D010446:Peptide Fragments; D018179:Receptors, Thrombin; C076901:thrombin receptor-activating peptide (P508-530); D013917:Thrombin; D002118:Calcium