Presence of functionally active protease-activated receptors 1 and 2 in myenteric glia.
Protease-activated receptors (PARs) belong to the family of membrane receptors coupled to G-proteins; their presence is reported in a wide variety of cells. The object of this study was to demonstrate the presence of PAR-1 and PAR-2 in myenteric glia of the guinea pig, and to elucidate the cellular mechanisms that are triggered upon receptor activation. Thrombin and PAR-1 agonist peptide (PARP-1) activate PAR-1 with a maximum mean +/- SEM change in intracellular calcium concentration with respect to basal level (Delta[Ca2+]i) of 183 +/- 18 nm and 169 +/- 6 nm, respectively. Trypsin and PAR-2 agonist peptide (PARP-2) activate PAR-2 with a maximum Delta[Ca2+]i of 364 +/- 28 nm and 239 +/- 19 nm, respectively. Inhibition of phospholipase C by U73312 (1 microm) decreased the Delta[Ca2+]i due to PAR-1 activation from 167 +/- 10 nm to 87 +/- 6 nm. The PAR-2-mediated Delta[Ca2+]i decreased from 193 +/- 10 nm to 124 +/- 8 nm when phospholipase C activity was inhibited. Blockade of sphingosine kinase with dimethylsphingosine (1 microm) decreased the Delta[Ca2+]i due to PAR-2 activation from 149 +/- 19 nm to 67 +/- 1 nm, but did not influence the PAR-1-mediated Delta[Ca2+]i. PAR-1 and PAR-2 were localized in myenteric glia by immunolabeling. Our results indicate that PAR-1 and PAR-2 are present in myenteric glia of the guinea pig, and their activation leads to increases in intracellular calcium via different signal transduction mechanisms that involve activation of phospholipase C and sphingosine kinase.
Garrido
Rosario
R
Department of Surgery, University of Michigan Medical Center, 1500 E. Medical Center Drive, Ann Arbor, MI 48109-0331, USA.
Segura
Bradley
B
Zhang
Weizhen
W
Mulholland
Michael
M
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005455:Fluorescent Antibody Technique; D006168:Guinea Pigs; D007424:Intracellular Fluid / Q000378:metabolism; D008297:Male; D009197:Myenteric Plexus / Q000166:cytology / Q000378:metabolism*; D009457:Neuroglia / Q000166:cytology / Q000378:metabolism*; D010455:Peptides / Q000494:pharmacology; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000037:antagonists & inhibitors; D016760:Proto-Oncogene Proteins c-fos / Q000096:biosynthesis; D044463:Receptor, PAR-1; D044464:Receptor, PAR-2; D018179:Receptors, Thrombin / Q000819:agonists / Q000096:biosynthesis*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D013917:Thrombin / Q000494:pharmacology; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors; D000099157:Sphingosine Kinase
D002118:Calcium; D004791:Enzyme Inhibitors; D010455:Peptides; D017853:Phosphotransferases (Alcohol Group Acceptor); D016760:Proto-Oncogene Proteins c-fos; D044463:Receptor, PAR-1; D044464:Receptor, PAR-2; D018179:Receptors, Thrombin; D013917:Thrombin; D010738:Type C Phospholipases; D000099157:Sphingosine Kinase