Endogenous cardiac troponin T modulates Ca2+-mediated smooth muscle contraction

Shunichi Kajioka, Fumi Takahashi-Yanaga, Nouval Shahab, Mitsuho Onimaru, Miho Matsuda, Ryosuke Takahashi, Haruhiko Asano, Hiromitsu Morita, Sachio Morimoto, Yoshikazu Yonemitsu, Maya Hayashi, Narihito Seki, Toshiuyki Sasaguri, Masato Hirata, Shinsuke Nakayama, Seiji Naito

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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 Ca2+ concentration ([Ca2+]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 Ca2+ -force relationship was shifted toward greater [Ca2+]i, indicating a sizeable contribution of cTnT to smooth muscle contraction at [Ca2+] 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.

Original languageEnglish
Article number979
JournalScientific reports
Volume2
DOIs
Publication statusPublished - Dec 1 2012

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