Thrombin receptor peptide inhibits thrombin-induced increase in endothelial permeability by receptor desensitization.
Thrombin, a potent activator of cellular responses, proteolytically cleaves, and thereby activates its receptor. In the present study, we compared the effects of the thrombin receptor 14-amino acid peptide (TRP-14; SFLLRNPNDKYEPF), which comprises the NH2 terminus after cleavage of the thrombin receptor, and of the native alpha-thrombin on endothelial monolayer permeability. Addition of TRP-14 (1-200 microM) to bovine pulmonary artery endothelial cells increased [Ca2+]i in a dose-dependent manner. The peak increase in [Ca2+]i in response to 100 microM TRP-14 or 0.1 microM alpha-thrombin was similar (i.e., 931 +/- 74 nM and 1032 +/- 80 nM, respectively), which was followed by a slow decrease with t1/2 values of 0.73 and 0.61 min, respectively. Extracellular Ca2+ chelation with 5 mM EGTA abolished the sustained increases in [Ca2+]i induced by either TRP-14 or alpha-thrombin. alpha-thrombin (0.1 microM) increased transendothelial [125I]albumin permeability, whereas TRP-14 (1-100 microM) had no effect. Coincubation of 100 microM TRP-14 with 1 microM DIP-alpha-thrombin also did not increase permeability over control values. Stimulation of BPAEC with 0.1 microM alpha-thrombin induced translocation of protein kinase C (PKC) from the cytosol to the plasma membrane indicative of PKC activation, whereas TRP-14 had no effect at any concentration. TRP-14 at 100 microM desensitized BPAEC to thrombin-induced increases in [Ca2+]i and transendothelial permeability. The Ca2+ desensitization was reversed after approximately 60 min, and this recovery paralleled the recovery of the permeability response. These findings indicate that the TRP-14-induced Ca2+ mobilization in the absence of PKC activation is insufficient to increase endothelial permeability. In contrast, the increase in endothelial permeability after alpha-thrombin occurred in conjunction with Ca2+ mobilization as well as PKC activation. TRP-14 pretreatment prevented the alpha-thrombin-induced increase in endothelial permeability secondary to desensitization of the Ca2+ signal. The results suggest that combined cytosolic Ca2+ mobilization mediated by TRP-14 and PKC activation mediated by a TRP-14-independent pathway are dual signals responsible for the thrombin-induced increase in vascular endothelial permeability.
Lum
H
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Department of Physiology, Albany Medical College, Union University, New York 12208.
Andersen
T T
TT
Siflinger-Birnboim
A
A
Tiruppathi
C
C
Goligorsky
M S
MS
Fenton
J W
JW
Malik
A B
AB
D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002417:Cattle; D002463:Cell Membrane Permeability / Q000187:drug effects; D002478:Cells, Cultured; D003600:Cytosol / Q000378:metabolism; D004730:Endothelium, Vascular / Q000187:drug effects / Q000502:physiology*; D007457:Iodine Radioisotopes; D007700:Kinetics; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000138:chemical synthesis / Q000494:pharmacology*; D011651:Pulmonary Artery; D011956:Receptors, Cell Surface / Q000378:metabolism / Q000502:physiology*; D018179:Receptors, Thrombin; D012710:Serum Albumin, Bovine / Q000378:metabolism; D013917:Thrombin / Q000494:pharmacology*
D007457:Iodine Radioisotopes; D010446:Peptide Fragments; D011956:Receptors, Cell Surface; D018179:Receptors, Thrombin; D012710:Serum Albumin, Bovine; D013917:Thrombin; D002118:Calcium