title: Endogenous cardiac troponin T modulates Ca(2+)-mediated smooth muscle contraction.
abstract: Mechanisms linked to actin filaments have long been thought to cooperate in smooth muscle contraction, although key molecules were unclear. We show evidence that cardiac troponin T (cTnT) substantially contributes to Ca(2+)-mediated contraction in a physiological range of cytosolic Ca(2+) concentration ([Ca(2+)](i)). cTnT was detected in various smooth muscles of the aorta, trachea, gut and urinary bladder, including in humans. Also, cTnT was distributed along with tropomyosin in smooth muscle cells, suggesting that these proteins are ready to cause smooth muscle contraction. In chemically permeabilised smooth muscle of cTnT(+/-) mice in which cTnT reduced to ~50%, the Ca(2+)-force relationship was shifted toward greater [Ca(2+)](i), indicating a sizeable contribution of cTnT to smooth muscle contraction at [Ca(2+)](i) < 1 μM. Furthermore, addition of supplemental TnI and TnC reconstructed a troponin system to enhance contraction. The results indicated that a Tn/Tn-like system on actin-filaments cooperates together with the thick-filament pathway.
authors.affiliation: Department of Urology, Kyushu University, Japan.
authors.forename: Shunichi
authors.initials: S
authors.lastname: Kajioka
authors.forename: Fumi
authors.initials: F
authors.lastname: Takahashi-Yanaga
authors.forename: Nouval
authors.initials: N
authors.lastname: Shahab
authors.forename: Mitsuho
authors.initials: M
authors.lastname: Onimaru
authors.forename: Miho
authors.initials: M
authors.lastname: Matsuda
authors.forename: Ryosuke
authors.initials: R
authors.lastname: Takahashi
authors.forename: Haruhiko
authors.initials: H
authors.lastname: Asano
authors.forename: Hiromitsu
authors.initials: H
authors.lastname: Morita
authors.forename: Sachio
authors.initials: S
authors.lastname: Morimoto
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Yonemitsu
authors.forename: Maya
authors.initials: M
authors.lastname: Hayashi
authors.forename: Narihito
authors.initials: N
authors.lastname: Seki
authors.forename: Toshiuyki
authors.initials: T
authors.lastname: Sasaguri
authors.forename: Masato
authors.initials: M
authors.lastname: Hirata
authors.forename: Shinsuke
authors.initials: S
authors.lastname: Nakayama
authors.forename: Seiji
authors.initials: S
authors.lastname: Naito
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000502:physiology*; D006321:Heart / Q000502:physiology*; D006801:Humans; D066298:In Vitro Techniques; D051379:Mice; D009119:Muscle Contraction / Q000502:physiology*; D009130:Muscle, Smooth / Q000502:physiology*; D014018:Tissue Distribution; D020107:Troponin T / Q000378:metabolism*
chemical_list: D020107:Troponin T; D002118:Calcium