Differential Ca2+responses induced by thrombin and thrombin-receptor agonist peptides in HSY-EA1 cells

Authors

  • Akihiko Tanimura,

    Corresponding author
    1. Department of Dental Pharmacology, School of Dentistry, Health Sciences University of Hokkaido, Ishikari-Tobetsu, Hokkaido 061-0293, Japan
      Corresponding author. Tel.: +81-1332-3-1211; fax: +81-1332-3-1399 tanimura@hoku-iryo-u.ac.jp
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  • Akiko Shitara,

    1. Department of Dental Pharmacology, School of Dentistry, Health Sciences University of Hokkaido, Ishikari-Tobetsu, Hokkaido 061-0293, Japan
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  • Akihiro Nezu,

    1. Department of Dental Pharmacology, School of Dentistry, Health Sciences University of Hokkaido, Ishikari-Tobetsu, Hokkaido 061-0293, Japan
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  • Takao Morita,

    1. Department of Dental Pharmacology, School of Dentistry, Health Sciences University of Hokkaido, Ishikari-Tobetsu, Hokkaido 061-0293, Japan
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  • Yosuke Tojyo

    1. Department of Dental Pharmacology, School of Dentistry, Health Sciences University of Hokkaido, Ishikari-Tobetsu, Hokkaido 061-0293, Japan
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Corresponding author. Tel.: +81-1332-3-1211; fax: +81-1332-3-1399 tanimura@hoku-iryo-u.ac.jp

Abstract

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 Ca2+responses in HSY-EA1 cells. Thrombin-induced increases in cytosolic Ca2+concentrations ([Ca2+]i) returned to basal levels within 60 s, but SFLLRN generated a sustained [Ca2+]ielevation. 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 [Ca2+]iin 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.

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