title: Amino acid mutations in the caldesmon COOH-terminal functional domain increase force generation in bladder smooth muscle.
abstract: Caldesmon (CaD), a component of smooth muscle thin filaments, binds actin, tropomyosin, calmodulin, and myosin and inhibits actin-activated ATP hydrolysis by smooth muscle myosin. Internal deletions of the chicken CaD functional domain that spans from amino acids (aa) 718 to 731, which corresponds to aa 512-530 including the adjacent aa sequence in mouse CaD, lead to diminished CaD-induced inhibition of actin-activated ATP hydrolysis by myosin. Transgenic mice with mutations of five aa residues (Lys(523) to Gln, Val(524) to Leu, Ser(526) to Thr, Pro(527) to Cys, and Lys(529) to Ser), which encompass the ATPase inhibitory determinants located in exon 12, were generated by homologous recombination. Homozygous (-/-) animals did not develop, but heterozygous (+/-) mice carrying the expected mutations in the CaD ATPase inhibitory domain (CaD mutant) matured and reproduced normally. The peak force produced in response to KCl and electrical field stimulation by the detrusor smooth muscle from the CaD mutant was high compared with that of the wild type. CaD mutant mice revealed nonvoiding contractions during bladder filling on awake cystometry, suggesting that the CaD ATPase inhibitory domain suppresses force generation during the filling phase and this suppression is partially released by mutations in 50% of CaD in heterozygous. Our data show for the first time a functional phenotype, at the intact smooth muscle tissue and in vivo organ levels, following mutation of a functional domain at the COOH-terminal region of CaD.
authors.affiliation: Dept. of Surgery and Dept. of Pathobiology, Univ. of Pennsylvania, 500 South Ridgeway Ave., Glenolden, PA 19036. chackosk@mail.med.upenn.edu.
authors.forename: Maoxian
authors.initials: M
authors.lastname: Deng
authors.forename: Ettickan
authors.initials: E
authors.lastname: Boopathi
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Hypolite
authors.forename: Tobias
authors.initials: T
authors.lastname: Raabe
authors.forename: Shaohua
authors.initials: S
authors.lastname: Chang
authors.forename: Stephen
authors.initials: S
authors.lastname: Zderic
authors.forename: Alan J
authors.initials: AJ
authors.lastname: Wein
authors.forename: Samuel
authors.initials: S
authors.lastname: Chacko
mesh_terms: D000818:Animals; D002148:Calmodulin-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002645:Chickens; D004558:Electric Stimulation; D006579:Heterozygote; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009119:Muscle Contraction / Q000187:drug effects; D053580:Muscle Strength / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects / Q000294:innervation / Q000378:metabolism*; D009154:Mutation; D009218:Myosins / Q000378:metabolism; D010641:Phenotype; D011189:Potassium Chloride / Q000494:pharmacology; D017434:Protein Structure, Tertiary; D013997:Time Factors; D001743:Urinary Bladder / Q000187:drug effects / Q000294:innervation / Q000378:metabolism*; D014563:Urodynamics
chemical_list: D002148:Calmodulin-Binding Proteins; D011189:Potassium Chloride; D009218:Myosins
keywords: actin; detrusor overactivity; myosin ATPase; smooth muscle cell; thin filament