General description

Proteinase-activated receptor 4 (UniProt Q96RI0; also known as Coagulation factor II receptor-like 3, PAR-4, Thrombin receptor-like 3) is encoded by the F2RL3 (also known as PAR4) gene (Gene ID 9002) in human. Protease-activated receptors (PARs) constitute a unique family of seven-transmembrane, G-protein-coupled receptors (GPCRs) activated by proteolytic cleavage of their N-terminal propeptide sequence. Once cleaved off, the N-terminal propeptide fragment functions as a ligand and activates the receptor by binding the second extracellular loop. The four PAR family members (PAR-1 to PAR-4) are widely expressed and activated by multiple proteases, and utilize different types of G-proteins (Gi, Gq, and G12/13) for signal transdution depending on the activating protease and cellular context. PAR-4 is expressed on platelets and exhibits a low-affinity for thrombin. However, PAR-4 is able to form hetero-oligomers with both PAR-1 and the ADP receptor P2Y12 to mediate thrombin- and ADP-initiated signaling. PAR-4 cleavage is significantly enhanced through hetero-oligomerization with PAR-1, and PAR-4 interaction with P2Y12 is directly linked to arrestin-2 recruitment and AKT signaling. PAR-4 is a 7-transmembrane (a.a. 83-103, 109-129, 152-172, 192-213, 248-268, 284-304, 320-343) GPCR activated by thrombin cleavage between R47 and G48, having 3 extracellular loops and 3 intracellular loops between the extracellular N-terminal end (a.a. 48-82) the cytoplasmic C-terminal tail (a.a. 344-385).

Specificity

Clone 14H6 recognizes an epitope near (C-terminal) to the thrombin-cleavage site. Unlike clone 5F10 (Cat. No. MABS1298), clone 14H6 does not protect cell surface PAR4 against thrombin cleavage (Mumaw, M.M., et al. (2015). Thromb. Res. 135(6):1165-1171). Clone 14H6 recognizes prepro- and pro-, but not proteolytically activated, human PAR4. A structual change at the cleavage site following thrombin cleavage is believed to prevent the detection of the activated PAR-4 by clone 5F10.

Immunogen

Epitope: Near (C-terminal to) the thrombin cleavage site.

Application

Anti-PAR4 Antibody, clone 14H6 is an antibody against PAR4 for use in Western Blotting, Immunocytochemistry, Flow Cytometry.

Immunocytochemistry Analysis: A representative lot detected the expression of exogenously transfected human PAR4 by fluorescent immunocytochemistry staining of 4% formaldehyde-fixed HEK293 Flp-In cells following tetracycline treatment (Mumaw, M.M., et al. (2015). Thromb. Res. 135(6):1165-1171).
Immunocytochemistry Analysis: A representative lot detected endogenous PAR4 by fluorescent immunocytochemistry staining of 4% formaldehyde-fixed human platelets. Thrombin treatment diminished PAR4 immunoreactivity (Mumaw, M.M., et al. (2015). Thromb. Res. 135(6):1165-1171)
Flow Cytometry Analysis: A representative lot detected tetracycline-induced expression of exogenously transfected human PAR4 on the surface of HEK293 Flp-In cells. Thrombin treatment diminished cell surface PAR4 immunoreactivity (Mumaw, M.M., et al. (2015). Thromb. Res. 135(6):1165-1171).
Western Blotting Analysis: A representative lot detected MBP fusion proteins containing human PAR4 fragment a.a. 18-78, 41-66, or 48-72. MBP-PAR4 fusion cleavage by thrombin ablolished target band detection by clone 14H6 (Mumaw, M.M., et al. (2015). Thromb. Res. 135(6):1165-1171).
Western Blotting Analysis: A representative lot detected tetracycline-induced expression of exogenously introduced human PAR4 in a HEK293 Flp-In cell line, as well as endogenous PAR4 in isolated human platelets (hPLTs). Thrombin activation of hPLTs diminished PAR4 target band detection (Mumaw, M.M., et al. (2015). Thromb. Res. 135(6):1165-1171).

Quality

Evaluated by Western Blotting in human platelet lysate.

Western Blotting Analysis: A 1:250 dilution of this antibody detected PAR4 in 50 µg of human platelet lysate.

Target description

~45 kDa observed. 41.13/39.16 kDa (prepro-/pro-PAR4) calculated. The broad banding pattern and larger apparent band size is consistent with the detection of glycosylated PAR4. Uncharacterized band(s) may appear in some lysates.