TY - JOUR
T1 - Cardiac resynchronization sensitizes the sarcomere to calcium by reactivating GSK-3?
AU - Kirk, Jonathan A.
AU - Holewinski, Ronald J.
AU - Kooij, Viola
AU - Agnetti, Giulio
AU - Tunin, Richard S.
AU - Witayavanitkul, Namthip
AU - De Tombe, Pieter P.
AU - Gao, Wei Dong
AU - Van Eyk, Jennifer
AU - Kass, David A.
PY - 2014/1/2
Y1 - 2014/1/2
N2 - Cardiac resynchronization therapy (CRT), the application of biventricular stimulation to correct discoordinate contraction, is the only heart failure treatment that enhances acute and chronic systolic function, increases cardiac work, and reduces mortality. Resting myocyte function also increases after CRT despite only modest improvement in calcium transients, suggesting that CRT may enhance myofilament calcium responsiveness. To test this hypothesis, we examined adult dogs subjected to tachypacing-induced heart failure for 6 weeks, concurrent with ventricular dyssynchrony (HFdys) or CRT. Myofilament force-calcium relationships were measured in skinned trabeculae and/or myocytes. Compared with control, maximal calcium-Activated force and calcium sensitivity declined globally in HFdys; however, CRT restored both. Phosphatase PP1 induced calcium desensitization in control and CRT-treated cells, while HFdys cells were unaffected, implying that CRT enhances myofilament phosphorylation. Proteomics revealed phosphorylation sites on Z-disk and M-band proteins, which were predicted to be targets of glycogen synthase kinase-3(GSK-3?). We found that GSK-3was deactivated in HFdys and reactivated by CRT. Mass spectrometry of myofilament proteins from HFdys animals incubated with GSK-3confirmed GSK-3?-dependent phosphorylation at many of the same sites observed with CRT. GSK-3restored calcium sensitivity in HFdys, but did not affect control or CRT cells. These data indicate that CRT improves calcium responsiveness of myofilaments following HFdys through GSK-3reactivation, identifying a therapeutic approach to enhancing contractile function.
AB - Cardiac resynchronization therapy (CRT), the application of biventricular stimulation to correct discoordinate contraction, is the only heart failure treatment that enhances acute and chronic systolic function, increases cardiac work, and reduces mortality. Resting myocyte function also increases after CRT despite only modest improvement in calcium transients, suggesting that CRT may enhance myofilament calcium responsiveness. To test this hypothesis, we examined adult dogs subjected to tachypacing-induced heart failure for 6 weeks, concurrent with ventricular dyssynchrony (HFdys) or CRT. Myofilament force-calcium relationships were measured in skinned trabeculae and/or myocytes. Compared with control, maximal calcium-Activated force and calcium sensitivity declined globally in HFdys; however, CRT restored both. Phosphatase PP1 induced calcium desensitization in control and CRT-treated cells, while HFdys cells were unaffected, implying that CRT enhances myofilament phosphorylation. Proteomics revealed phosphorylation sites on Z-disk and M-band proteins, which were predicted to be targets of glycogen synthase kinase-3(GSK-3?). We found that GSK-3was deactivated in HFdys and reactivated by CRT. Mass spectrometry of myofilament proteins from HFdys animals incubated with GSK-3confirmed GSK-3?-dependent phosphorylation at many of the same sites observed with CRT. GSK-3restored calcium sensitivity in HFdys, but did not affect control or CRT cells. These data indicate that CRT improves calcium responsiveness of myofilaments following HFdys through GSK-3reactivation, identifying a therapeutic approach to enhancing contractile function.
UR - http://www.scopus.com/inward/record.url?scp=84892934846&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84892934846&partnerID=8YFLogxK
U2 - 10.1172/JCI69253
DO - 10.1172/JCI69253
M3 - Article
C2 - 24292707
AN - SCOPUS:84892934846
SN - 0021-9738
VL - 124
SP - 129
EP - 139
JO - Journal of Clinical Investigation
JF - Journal of Clinical Investigation
IS - 1
ER -