TY - JOUR
T1 - Lysine acetylation of F-actin decreases tropomyosin-based inhibition of actomyosin activity
AU - Schmidt, William
AU - Madan, Aditi
AU - Brian Foster, D.
AU - Cammarato, Anthony
N1 - Funding Information:
Funding and additional information—This work was supported by National Institutes of Health Grants R01HL134821 (to D. B. F.) and R01HL124091 (to A. C.), American Heart Association Grants 18TPA34170575 (to D. B. F.) and 17POST33630159 (to W. S.), and a Johns Hopkins University Catalyst Award (to D. B. F.). The content is solely the responsibility of the authors and does not neces- sarily represent the official views of the National Institutes of Health.
Publisher Copyright:
© 2020 Schmidt et al.
PY - 2020/11/13
Y1 - 2020/11/13
N2 - Recent proteomics studies of vertebrate striated muscle have identified lysine acetylation at several sites on actin. Acetylation is a reversible post-translational modification that neutralizes lysine’s positive charge. Positively charged residues on actin, particularly Lys326 and Lys328, are predicted to form critical electrostatic interactions with tropomyosin (Tpm) that promote its binding to filamentous (F)-actin and bias Tpm to an azimuthal location where it impedes myosin attachment. The troponin (Tn) complex also influences Tpm’s position along F-actin as a function of Ca21 to regulate exposure of myosin-binding sites and, thus, myosin cross-bridge recruitment and force production. Interestingly, Lys326 and Lys328 are among the documented acetylated residues. Using an acetic anhydride-based labeling approach, we showed that excessive, nonspecific actin acetylation did not disrupt characteristic F-actin–Tpm binding. However, it significantly reduced Tpm-mediated inhibition of myosin attachment, as reflected by increased F-actin–Tpm motility that persisted in the presence of Tn and submaximal Ca21. Furthermore, decreasing the extent of chemical acetylation, to presumptively target highly reactive Lys326 and Lys328, also resulted in less inhibited F-actin–Tpm, implying that modifying only these residues influences Tpm’s location and, potentially, thin filament regulation. To unequivocally determine the residue-specific consequences of acetylation on Tn–Tpm–based regulation of actomyosin activity, we assessed the effects of K326Q and K328Q acetyl (Ac)-mimetic actin on Ca21-dependent, in vitro motility parameters of reconstituted thin filaments (RTFs). Incorporation of K328Q actin significantly enhanced Ca21 sensitivity of RTF activation relative to control. Together, our findings suggest that actin acetylation, especially Lys328, modulates muscle contraction via disrupting inhibitory Tpm positioning.
AB - Recent proteomics studies of vertebrate striated muscle have identified lysine acetylation at several sites on actin. Acetylation is a reversible post-translational modification that neutralizes lysine’s positive charge. Positively charged residues on actin, particularly Lys326 and Lys328, are predicted to form critical electrostatic interactions with tropomyosin (Tpm) that promote its binding to filamentous (F)-actin and bias Tpm to an azimuthal location where it impedes myosin attachment. The troponin (Tn) complex also influences Tpm’s position along F-actin as a function of Ca21 to regulate exposure of myosin-binding sites and, thus, myosin cross-bridge recruitment and force production. Interestingly, Lys326 and Lys328 are among the documented acetylated residues. Using an acetic anhydride-based labeling approach, we showed that excessive, nonspecific actin acetylation did not disrupt characteristic F-actin–Tpm binding. However, it significantly reduced Tpm-mediated inhibition of myosin attachment, as reflected by increased F-actin–Tpm motility that persisted in the presence of Tn and submaximal Ca21. Furthermore, decreasing the extent of chemical acetylation, to presumptively target highly reactive Lys326 and Lys328, also resulted in less inhibited F-actin–Tpm, implying that modifying only these residues influences Tpm’s location and, potentially, thin filament regulation. To unequivocally determine the residue-specific consequences of acetylation on Tn–Tpm–based regulation of actomyosin activity, we assessed the effects of K326Q and K328Q acetyl (Ac)-mimetic actin on Ca21-dependent, in vitro motility parameters of reconstituted thin filaments (RTFs). Incorporation of K328Q actin significantly enhanced Ca21 sensitivity of RTF activation relative to control. Together, our findings suggest that actin acetylation, especially Lys328, modulates muscle contraction via disrupting inhibitory Tpm positioning.
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U2 - 10.1074/jbc.RA120.015277
DO - 10.1074/jbc.RA120.015277
M3 - Article
C2 - 32873710
AN - SCOPUS:85096202972
SN - 0021-9258
VL - 295
SP - 15527
EP - 15539
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 46
ER -