title: Molecular cloning of the rat proteinase-activated receptor 4 (PAR4).
abstract: BACKGROUND
  The proteinase-activated receptor 4 (PAR4) is a G-protein-coupled receptor activated by proteases such as thrombin and trypsin. Although activation of PAR4 has been shown to modulate rat gastrointestinal motility, the rat PAR4 sequence was unknown until now. This study aimed to identify the rat PAR4 cDNA.
  
  
  RESULTS
  The cDNA coding for the rat PAR4 homologue was cloned from the duodenum. Northern blots demonstrated a 3.0 kb transcript in the duodenum. Protein homology with mouse and human counterparts was 90% and 75% respectively. PAR4 is expressed predominantly in the esophagus, stomach, duodenum and the spleen. When expressed in COS cells, PAR4 is activated by trypsin (1 nM), thrombin (50 nM), mouse PAR4 specific peptide (500 microM) and a putative rat PAR4 specific activating peptide (100 microM), as measured by intracellular Ca2+-changes.
  
  
  CONCLUSIONS
  We have identified and characterized cDNA encoding the rat PAR4 homologue. PAR4 is expressed predominantly in the upper gastrointestinal tract. It is activated by trypsin, thrombin and its newly identified rat PAR4 specific activating peptide.
authors.affiliation: Enteric Neuromuscular Disorders and Pain Laboratory, Division of Gastroenterology and Hepatology, University of Texas Medical Branch, Galveston, TX, USA. wahooger@utmb.edu
authors.forename: Willemijntje A
authors.initials: WA
authors.lastname: Hoogerwerf
authors.forename: Helen Lee
authors.initials: HL
authors.lastname: Hellmich
authors.forename: Maria Adelaide
authors.initials: MA
authors.lastname: Micci
authors.forename: John H
authors.initials: JH
authors.lastname: Winston
authors.forename: Lei
authors.initials: L
authors.lastname: Zou
authors.forename: Pankaj J
authors.initials: PJ
authors.lastname: Pasricha