Role of junctophilins on excitation-contraction coupling of skeletal muscles

• Project/Area Number: 16K08491
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: General physiology
• Research Institution: Shinshu University
• Principal Investigator: Nakada Tsutomu 信州大学, 学術研究院総合人間科学系, 准教授 (70452141)
• Project Period (FY): 2016-04-01 – 2019-03-31
• Project Status: Completed (Fiscal Year 2018)
• Budget Amount: ¥4,810,000 (Direct Cost: ¥3,700,000、Indirect Cost: ¥1,110,000); Fiscal Year 2018: ¥1,560,000 (Direct Cost: ¥1,200,000、Indirect Cost: ¥360,000); Fiscal Year 2017: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000); Fiscal Year 2016: ¥1,950,000 (Direct Cost: ¥1,500,000、Indirect Cost: ¥450,000)
• Keywords: 興奮収縮連関 / 骨格筋 / L型カルシウムチャネル / ジャンクトフィリン / リアノジン受容体 / 結合膜構造 / カルシウムチャネル

Outline of Final Research Achievements

Close physical association of CaV1.1 L-type calcium channels (LTCCs) at the sarcolemmal junctional membrane (JM) with ryanodine receptors of the sarcoplasmic reticulum (SR) is crucial for excitation-contraction coupling in skeletal muscle. However, the molecular mechanism underlying the JM targeting of LTCCs is unexplored. Junctophilins (JPs) 1 and 2 stabilize the JM by bridging the sarcolemmal and SR membranes. A JP1 mutant lacking the C-terminus including the transmembrane domain (JP1ΔCT) interacted with the sarcolemmal/T-tubule membrane but not the SR membrane. Expression of this mutant in adult mouse muscles impairing LTCC-JP coupling at triads, and substantially reducing Ca2+ transients without affecting SR Ca2+ content. Moreover, the contractile force of the JP1ΔCT-expressed muscle was dramatically reduced compared with the control. Taken together, JPs recruit LTCCs to the JM through physical interaction and ensure robust ECC at triads in skeletal muscle.

Academic Significance and Societal Importance of the Research Achievements

本研究では，骨格筋L型カルシウムチャネルの結合膜構造への集積が，ジャンクトフィリンとの直接的な結合によって調節されていることを，生体を用いた実験で初めて示した。骨格筋の収縮メカニズムを理解することは，正常状態の筋生理のみならず，様々な病態生理を説明する上で重要である。また，骨格筋と心筋の結合膜構造には多くの共通点があり，本研究で得られた知見は，心筋の収縮機構についても応用される可能性がある。

Research Products

• [Journal Article] Increase in phospholamban content in mouse skeletal muscle after denervation (2018)
  • Author(s): Masatoshi Komatsu, Tsutomu Nakada, Hiroyuki Kawagishi, Hiroyuki Kato, Mitsuhiko Yamada.
  • Journal Title: Journal of Muscle Research and Cell Motility Volume: 39 Issue: 5-6 Pages: 163-173
  • DOI: 10.1007/s10974-019-09504-2
  • Peer Reviewed
• [Journal Article] Physical interaction of junctophilin and the CaV1.1 C terminus is crucial for skeletal muscle contraction (2018)
  • Author(s): Nakada Tsutomu、Kashihara Toshihide、Komatsu Masatoshi、Kojima Katsuhiko、Takeshita Toshikazu、Yamada Mitsuhiko
  • Journal Title: Proceedings of the National Academy of Sciences Volume: 115 Issue: 17 Pages: 4507-4512
  • DOI: 10.1073/pnas.1716649115
  • Peer Reviewed / Open Access
• [Presentation] Interaction of junctophilins and the CaV1.1 is essential for the skeletal muscle contraction (2019)
  • Author(s): Tsutomu Nakada
  • Organizer: The 9th Federation of the Asian and Oceanian Physiological Societies Congress
  • Int'l Joint Research
• [Presentation] Interaction of junctophilins and the C-terminus of CaV1.1 subunits regulates localization and function of L-type calcium channels in skeletal muscle. (2017)
  • Author(s): Tsutomu Nakada, Masatoshi Komatsu, Toshihide Kashihara, Mitsuhiko Yamada
  • Organizer: Biophysical Society 61st Annual Meeting
  • Place of Presentation: New Orleans, USA
  • Year and Date: 2017-02-11
  • Int'l Joint Research
• [Presentation] Interaction of junctophilins and the C-terminus of CaV1.1 subunits regulates localization and function of L-type calcium channels in skeletal muscle. (2017)
  • Author(s): Tsutomu Nakada
  • Organizer: 20th International Symposium on Calcium Binding Proteins and Calcium Function In Health and Disease
  • Int'l Joint Research