TY - JOUR
T1 - Altered Contractility of Skeletal Muscle in Mice Deficient in Titin's M-Band Region
AU - Ottenheijm, Coen A.C.
AU - Hidalgo, Carlos
AU - Rost, Katharina
AU - Gotthardt, Michael
AU - Granzier, Henk
N1 - Funding Information:
We thank Dr. Furst for kindly providing the MyBP-C antibody, Dr. Siegfried Labeit for kindly providing the antibodies X148a-149 against MURF-1 and 1867/07#5 against sarcolipin, and Dr. Szczesna for providing the skeletal muscle troponin and light chain-2 proteins. We are grateful to Diana Acuna, Luann Wyly, Eric Rogers, and Gem Stark for expert technical assistance. This work was supported by a Rubicon postdoctoral grant from the Dutch Organization for Scientific Research to C.O., by the German Research Foundation (DFG, KFO 192) to M.G., and by U.S. National Institutes of Health grant HL062881 to H.G. Dr. Henk Granzier is the Allan and Alfie Norville Endowed Chair in Heart Disease in Women Research.
PY - 2009/10/16
Y1 - 2009/10/16
N2 - We investigated the contractile phenotype of skeletal muscle deficient in exons MEx1 and MEx2 (KO) of the titin M-band by using the cre-lox recombination system and a multidisciplinary physiological approach to study skeletal muscle contractile performance. At a maximal tetanic stimulation frequency, intact KO extensor digitorum longus muscle was able to produce wild-type levels of force. However, at submaximal stimulation frequency, force was reduced in KO mice, giving rise to a rightward shift of the force-frequency curve. This rightward shift of the force-frequency curve could not be explained by altered sarcoplasmic reticulum Ca2+ handling, as indicated by analysis of Ca2+ transients in intact myofibers and expression of Ca2+-handling proteins, but can be explained by the reduced myofilament Ca2+ sensitivity of force generation that we found. Western blotting experiments suggested that the excision of titin exons MEx1 and MEx2 did not result in major changes in expression of titin M-band binding proteins or phosphorylation level of the thin-filament regulatory proteins, but rather in a shift toward expression of slow isoforms of the thick-filament-associated protein, myosin binding protein-C. Extraction of myosin binding protein-C from skinned muscle normalized myofilament Ca2+ sensitivity of the KO extensor digitorum longus muscle. Thus, our data suggest that the M-band region of titin affects the expression of genes involved in the regulation of skeletal muscle contraction.
AB - We investigated the contractile phenotype of skeletal muscle deficient in exons MEx1 and MEx2 (KO) of the titin M-band by using the cre-lox recombination system and a multidisciplinary physiological approach to study skeletal muscle contractile performance. At a maximal tetanic stimulation frequency, intact KO extensor digitorum longus muscle was able to produce wild-type levels of force. However, at submaximal stimulation frequency, force was reduced in KO mice, giving rise to a rightward shift of the force-frequency curve. This rightward shift of the force-frequency curve could not be explained by altered sarcoplasmic reticulum Ca2+ handling, as indicated by analysis of Ca2+ transients in intact myofibers and expression of Ca2+-handling proteins, but can be explained by the reduced myofilament Ca2+ sensitivity of force generation that we found. Western blotting experiments suggested that the excision of titin exons MEx1 and MEx2 did not result in major changes in expression of titin M-band binding proteins or phosphorylation level of the thin-filament regulatory proteins, but rather in a shift toward expression of slow isoforms of the thick-filament-associated protein, myosin binding protein-C. Extraction of myosin binding protein-C from skinned muscle normalized myofilament Ca2+ sensitivity of the KO extensor digitorum longus muscle. Thus, our data suggest that the M-band region of titin affects the expression of genes involved in the regulation of skeletal muscle contraction.
KW - Ca sensitivity
KW - M-band
KW - skeletal muscle
KW - titin
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U2 - 10.1016/j.jmb.2009.08.009
DO - 10.1016/j.jmb.2009.08.009
M3 - Article
C2 - 19683008
AN - SCOPUS:70349243064
SN - 0022-2836
VL - 393
SP - 10
EP - 26
JO - Journal of Molecular Biology
JF - Journal of Molecular Biology
IS - 1
ER -