Abstract
Mutations in cardiac myosin binding protein C (cMyBP-C), a thick filament protein that modulates contraction of the heart, are a leading cause of hypertrophic cardiomyopathy (HCM). Electron microscopy and 3D reconstruction of thin filaments decorated with cMyBP-C N-terminal fragments suggest that one mechanism of this modulation involves the interaction of cMyBP-C's N-terminal domains with thin filaments to enhance their Ca2+-sensitivity by displacement of tropomyosin from its blocked (low Ca2+) to its closed (high Ca2+) position. The extent of this tropomyosin shift is reduced when cMyBP-C N-terminal domains are phosphorylated. In the current study, we have examined L348P, a sequence variant of cMyBP-C first identified in a screen of patients with HCM. In L348P, leucine 348 is replaced by proline in cMyBP-C's regulatory M-domain, resulting in an increase in cMyBP-C's ability to enhance thin filament Ca2+-sensitization. Our goal here was to determine the structural basis for this enhancement by carrying out 3D reconstruction of thin filaments decorated with L348P-mutant cMyBP-C. When thin filaments were decorated with wild type N-terminal domains at low Ca2+, tropomyosin moved from the blocked to the closed position, as found previously. In contrast, the L348P mutant caused a significantly larger tropomyosin shift, to approximately the open position, consistent with its enhancement of Ca2+-sensitization. Phosphorylated wild type fragments showed a smaller shift than unphosphorylated fragments, whereas the shift induced by the L348P mutant was not affected by phosphorylation. We conclude that the L348P mutation causes a gain of function by enhancing tropomyosin displacement on the thin filament in a phosphorylation-independent way.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 141-147 |
| Number of pages | 7 |
| Journal | Journal of Molecular and Cellular Cardiology |
| Volume | 91 |
| DOIs | |
| State | Published - Feb 1 2016 |
| Externally published | Yes |
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Keywords
- Cardiac muscle
- CMyBP-C
- Electron microscopy
- Hypertrophic cardiomyopathy
- Myosin binding protein C
- Thin filament
ASJC Scopus subject areas
- Molecular Biology
- Cardiology and Cardiovascular Medicine
Cite this
The cMyBP-C HCM variant L348P enhances thin filament activation through an increased shift in tropomyosin position. / Mun, Ji Young; Kensler, Robert W.; Harris, Samantha P.; Craig, Roger.
In: Journal of Molecular and Cellular Cardiology, Vol. 91, 01.02.2016, p. 141-147.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - The cMyBP-C HCM variant L348P enhances thin filament activation through an increased shift in tropomyosin position
AU - Mun, Ji Young
AU - Kensler, Robert W.
AU - Harris, Samantha P.
AU - Craig, Roger
PY - 2016/2/1
Y1 - 2016/2/1
N2 - Mutations in cardiac myosin binding protein C (cMyBP-C), a thick filament protein that modulates contraction of the heart, are a leading cause of hypertrophic cardiomyopathy (HCM). Electron microscopy and 3D reconstruction of thin filaments decorated with cMyBP-C N-terminal fragments suggest that one mechanism of this modulation involves the interaction of cMyBP-C's N-terminal domains with thin filaments to enhance their Ca2+-sensitivity by displacement of tropomyosin from its blocked (low Ca2+) to its closed (high Ca2+) position. The extent of this tropomyosin shift is reduced when cMyBP-C N-terminal domains are phosphorylated. In the current study, we have examined L348P, a sequence variant of cMyBP-C first identified in a screen of patients with HCM. In L348P, leucine 348 is replaced by proline in cMyBP-C's regulatory M-domain, resulting in an increase in cMyBP-C's ability to enhance thin filament Ca2+-sensitization. Our goal here was to determine the structural basis for this enhancement by carrying out 3D reconstruction of thin filaments decorated with L348P-mutant cMyBP-C. When thin filaments were decorated with wild type N-terminal domains at low Ca2+, tropomyosin moved from the blocked to the closed position, as found previously. In contrast, the L348P mutant caused a significantly larger tropomyosin shift, to approximately the open position, consistent with its enhancement of Ca2+-sensitization. Phosphorylated wild type fragments showed a smaller shift than unphosphorylated fragments, whereas the shift induced by the L348P mutant was not affected by phosphorylation. We conclude that the L348P mutation causes a gain of function by enhancing tropomyosin displacement on the thin filament in a phosphorylation-independent way.
AB - Mutations in cardiac myosin binding protein C (cMyBP-C), a thick filament protein that modulates contraction of the heart, are a leading cause of hypertrophic cardiomyopathy (HCM). Electron microscopy and 3D reconstruction of thin filaments decorated with cMyBP-C N-terminal fragments suggest that one mechanism of this modulation involves the interaction of cMyBP-C's N-terminal domains with thin filaments to enhance their Ca2+-sensitivity by displacement of tropomyosin from its blocked (low Ca2+) to its closed (high Ca2+) position. The extent of this tropomyosin shift is reduced when cMyBP-C N-terminal domains are phosphorylated. In the current study, we have examined L348P, a sequence variant of cMyBP-C first identified in a screen of patients with HCM. In L348P, leucine 348 is replaced by proline in cMyBP-C's regulatory M-domain, resulting in an increase in cMyBP-C's ability to enhance thin filament Ca2+-sensitization. Our goal here was to determine the structural basis for this enhancement by carrying out 3D reconstruction of thin filaments decorated with L348P-mutant cMyBP-C. When thin filaments were decorated with wild type N-terminal domains at low Ca2+, tropomyosin moved from the blocked to the closed position, as found previously. In contrast, the L348P mutant caused a significantly larger tropomyosin shift, to approximately the open position, consistent with its enhancement of Ca2+-sensitization. Phosphorylated wild type fragments showed a smaller shift than unphosphorylated fragments, whereas the shift induced by the L348P mutant was not affected by phosphorylation. We conclude that the L348P mutation causes a gain of function by enhancing tropomyosin displacement on the thin filament in a phosphorylation-independent way.
KW - Cardiac muscle
KW - CMyBP-C
KW - Electron microscopy
KW - Hypertrophic cardiomyopathy
KW - Myosin binding protein C
KW - Thin filament
UR - http://www.scopus.com/inward/record.url?scp=84953396946&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84953396946&partnerID=8YFLogxK
U2 - 10.1016/j.yjmcc.2015.12.014
DO - 10.1016/j.yjmcc.2015.12.014
M3 - Article
C2 - 26718724
AN - SCOPUS:84953396946
VL - 91
SP - 141
EP - 147
JO - Journal of Molecular and Cellular Cardiology
JF - Journal of Molecular and Cellular Cardiology
SN - 0022-2828
ER -