TY - JOUR

T1 - The molecular mechanisms of a high Ca2+-sensitivity and muscle weakness associated with the Ala155Thr substitution in Tpm3.12

AU - Avrova, Stanislava V.

AU - Karpicheva, Olga E.

AU - Simonyan, Armen O.

AU - Sirenko, Vladimir V.

AU - Redwood, Charles S.

AU - Borovikov, Y. S.

PY - 2019/7/23

Y1 - 2019/7/23

N2 - Substitution of Ala for Thr residue in 155th position in γ-tropomyosin (Tpm3.12) is associated with muscle weakness. To understand the mechanisms of this defect, we studied the Ca 2+-sensitivity of thin filaments in solution and multistep changes in mobility and spatial arrangement of actin, Tpm, and myosin heads during the ATPase cycle in reconstituted muscle fibres, using the polarized fluorescence microscopy. It was shown that the Ala155Thr (A155T) mutation increased the Ca 2+-sensitivity of the thin filaments in solution. In the absence of the myosin heads in the muscle fibres, the mutation did not alter the ability of troponin to switch the thin filaments on and off at high and low Ca 2+, respectively. However, upon the binding of myosin heads to the thin filaments at low Ca 2+, the mutant Tpm was found to be markedly closer to the open position, than the wild-type Tpm. In the presence of the mutant Tpm, switching on of actin monomers and formation of the strong-binding state of the myosin heads were observed at low Ca 2+, which indicated a higher myofilament Ca 2+-sensitivity. The mutation decreased the amount of myosin heads bound strongly to actin at high Ca 2+ and increased the number of these heads at relaxation. It is suggested that direct binding of myosin to Tpm may be one оf the reasons for muscle weakness associated with the A155T mutation. The use of reagents that decrease the Ca 2+-sensitivity of the troponin complex may not be adequate to restore muscle function in patients with the A155T mutation.

AB - Substitution of Ala for Thr residue in 155th position in γ-tropomyosin (Tpm3.12) is associated with muscle weakness. To understand the mechanisms of this defect, we studied the Ca 2+-sensitivity of thin filaments in solution and multistep changes in mobility and spatial arrangement of actin, Tpm, and myosin heads during the ATPase cycle in reconstituted muscle fibres, using the polarized fluorescence microscopy. It was shown that the Ala155Thr (A155T) mutation increased the Ca 2+-sensitivity of the thin filaments in solution. In the absence of the myosin heads in the muscle fibres, the mutation did not alter the ability of troponin to switch the thin filaments on and off at high and low Ca 2+, respectively. However, upon the binding of myosin heads to the thin filaments at low Ca 2+, the mutant Tpm was found to be markedly closer to the open position, than the wild-type Tpm. In the presence of the mutant Tpm, switching on of actin monomers and formation of the strong-binding state of the myosin heads were observed at low Ca 2+, which indicated a higher myofilament Ca 2+-sensitivity. The mutation decreased the amount of myosin heads bound strongly to actin at high Ca 2+ and increased the number of these heads at relaxation. It is suggested that direct binding of myosin to Tpm may be one оf the reasons for muscle weakness associated with the A155T mutation. The use of reagents that decrease the Ca 2+-sensitivity of the troponin complex may not be adequate to restore muscle function in patients with the A155T mutation.

KW - ATPase activity of myosin

KW - Ca -sensitivity

KW - Congenital myopathy

KW - Muscle fibre

KW - Mutation in tropomyosin

KW - Regulation of muscle contraction

KW - MYOSIN

KW - Ca2+-sensitivity

KW - ACTIN-FILAMENTS

KW - TROPOMYOSIN

KW - FLUORESCENCE

KW - RIGOR

KW - MUTATIONS

KW - TROPONIN

UR - http://www.scopus.com/inward/record.url?scp=85066249098&partnerID=8YFLogxK

UR - http://www.mendeley.com/research/molecular-mechanisms-high-ca2sensitivity-muscle-weakness-associated-ala155thr-substitution-tpm312

U2 - 10.1016/j.bbrc.2019.05.146

DO - 10.1016/j.bbrc.2019.05.146

M3 - Article

VL - 515

SP - 372

EP - 377

JO - Biochemical and Biophysical Research Communications

JF - Biochemical and Biophysical Research Communications

SN - 0006-291X

IS - 2

ER -