title: Involvement of rho p21 in the GTP-enhanced calcium ion sensitivity of smooth muscle contraction.
abstract: In the rabbit mesenteric arterial smooth muscle skinned by saponin, Ca2+ induced contraction in a concentration-dependent manner. Guanosine 5'-(3-O-thio)triphosphate (GTP gamma S), a non-hydrolyzable GTP analogue, lowered the Ca2+ concentrations required for this contraction and increased the Ca2+ sensitivity of the skinned smooth muscle contraction. GTP gamma S alone did not induce the contraction in the absence of Ca2+. This GTP gamma S-enhanced Ca2+ sensitivity was completely abolished by an exoenzyme of Staphylococcus aureus, named EDIN, and an exoenzyme of Clostridium botulinum, named C3, both of which are known to ADP-ribosylate the rho p21 family that belongs to the ras p21-like small GTP-binding protein superfamily. The GTP gamma S-bound form of rhoA p21 overcame the inhibitory action of EDIN. smg p21B, another small GTP-binding protein, was inactive. EDIN ADP-ribosylated a protein, which was most likely to be rho p21, in the skinned smooth muscle. The GTP gamma S-bound form of rhoA p21, but not the GDP-bound form, substituted for GTP gamma S and enhanced the Ca2+ sensitivity of the skinned smooth muscle contraction. smg p21B was inactive. These results indicate that rhoA p21 is involved in the GTP gamma S-enhanced Ca2+ sensitivity of the smooth muscle contraction.
authors.affiliation: Department of Biochemistry, Kobe University School of Medicine, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Hirata
authors.forename: A
authors.initials: A
authors.lastname: Kikuchi
authors.forename: T
authors.initials: T
authors.lastname: Sasaki
authors.forename: S
authors.initials: S
authors.lastname: Kuroda
authors.forename: K
authors.initials: K
authors.lastname: Kaibuchi
authors.forename: Y
authors.initials: Y
authors.lastname: Matsuura
authors.forename: H
authors.initials: H
authors.lastname: Seki
authors.forename: K
authors.initials: K
authors.lastname: Saida
authors.forename: Y
authors.initials: Y
authors.lastname: Takai
mesh_terms: D000246:Adenosine Diphosphate Ribose / Q000378:metabolism; D000818:Animals; D001426:Bacterial Proteins / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D002413:Cations, Divalent; D004591:Electrophoresis, Polyacrylamide Gel; D019204:GTP-Binding Proteins / Q000378:metabolism*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D006153:Guanosine Diphosphate / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism*; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D009131:Muscle, Smooth, Vascular / Q000378:metabolism / Q000502:physiology*; D011817:Rabbits; D013211:Staphylococcus aureus / Q000201:enzymology; D020742:rhoA GTP-Binding Protein
chemical_list: D001426:Bacterial Proteins; D002413:Cations, Divalent; C067120:epidermal cell differentiation inhibitor, Staphylococcus aureus; D006153:Guanosine Diphosphate; D000246:Adenosine Diphosphate Ribose; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D006160:Guanosine Triphosphate; D019204:GTP-Binding Proteins; D020742:rhoA GTP-Binding Protein; D002118:Calcium