Differential Ca(2+)responses induced by thrombin and thrombin-receptor agonist peptides in HSY-EA1 cells.
We examined the mechanism by which protease-activated receptor (PAR)-1 is desensitized by comparing the effect of thrombin and the soluble agonist peptide SFLLRN on Ca(2+)responses in HSY-EA1 cells. Thrombin-induced increases in cytosolic Ca(2+)concentrations ([Ca(2+)](i)) returned to basal levels within 60 s, but SFLLRN generated a sustained [Ca(2+)](i)elevation. Interestingly, thrombin-desensitized cells partially retained their ability to respond to SFLLRN. We desensitized PAR-2 by pretreating cells with SLIGKV to confirm that this response was not due to PAR-2, which can recognize SFLLRN. The highly specific PAR-1 agonist peptide TFLLR also increased [Ca(2+)](i)in PAR-2-desensitized cells pretreated with thrombin. These observations indicate that thrombin disarms PAR-1 from further proteolytic activation, but leaves the receptor responsive for non-tethered ligands.
Tanimura
Akihiko
A
Department of Dental Pharmacology, School of Dentistry, Health Sciences University of Hokkaido, Ishikari-Tobetsu, Hokkaido 061-0293, Japan. tanimura@hoku-iryo-u.ac.jp
Shitara
Akiko
A
Nezu
Akihiro
A
Morita
Takao
T
Tojyo
Yosuke
Y
D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D006801:Humans; D008024:Ligands; D009842:Oligopeptides / Q000494:pharmacology; D010446:Peptide Fragments / Q000494:pharmacology; D010455:Peptides / Q000737:chemistry; D044463:Receptor, PAR-1 / Q000378:metabolism; D044464:Receptor, PAR-2 / Q000378:metabolism; D018179:Receptors, Thrombin / Q000378:metabolism*; D013917:Thrombin / Q000378:metabolism*; D013997:Time Factors
D008024:Ligands; D009842:Oligopeptides; C462999:PAR-1-activating peptide; D010446:Peptide Fragments; D010455:Peptides; D044463:Receptor, PAR-1; D044464:Receptor, PAR-2; D018179:Receptors, Thrombin; C082835:thrombin receptor peptide (42-47); D013917:Thrombin; D002118:Calcium