TY - JOUR
T1 - PPP1R12C Promotes Atrial Hypocontractility in Atrial Fibrillation
AU - Perike, Srikanth
AU - Gonzalez-Gonzalez, Francisco J.
AU - Abu-Taha, Issam
AU - Damen, Frederick W.
AU - Hanft, Laurin M.
AU - Lizama, Ken S.
AU - Aboonabi, Anahita
AU - Capote, Andrielle E.
AU - Aguilar-Sanchez, Yuriana
AU - Levin, Benjamin
AU - Han, Zhenbo
AU - Sridhar, Arvind
AU - Grand, Jacob
AU - Martin, Jody
AU - Akar, Joseph G.
AU - Warren, Chad M.
AU - John Solaro, R.
AU - Ong, Sang Ging
AU - Darbar, Dawood
AU - McDonald, Kerry S.
AU - Goergen, Craig J.
AU - Wolska, Beata M.
AU - Dobrev, Dobromir
AU - Wehrens, Xander H.T.
AU - McCauley, Mark D.
N1 - Publisher Copyright:
© 2023 American Heart Association, Inc.
PY - 2023/10/13
Y1 - 2023/10/13
N2 - BACKGROUND: Atrial fibrillation (AF) - the most common sustained cardiac arrhythmia - increases thromboembolic stroke risk 5-fold. Although atrial hypocontractility contributes to stroke risk in AF, the molecular mechanisms reducing myofilament contractile function remain unknown. We tested the hypothesis that increased expression of PPP1R12C (protein phosphatase 1 regulatory subunit 12C) - the PP1 (protein phosphatase 1) regulatory subunit targeting MLC2a (atrial myosin light chain 2) - causes hypophosphorylation of MLC2a and results in atrial hypocontractility. METHODS: Right atrial appendage tissues were isolated from human patients with AF versus sinus rhythm controls. Western blots, coimmunoprecipitation, and phosphorylation studies were performed to examine how the PP1c (PP1 catalytic subunit)-PPP1R12C interaction causes MLC2a dephosphorylation. In vitro studies of pharmacological MRCK (myotonic dystrophy kinase-related Cdc42-binding kinase) inhibitor (BDP5290) in atrial HL-1 cells were performed to evaluate PP1 holoenzyme activity on MLC2a. Cardiac-specific lentiviral PPP1R12C overexpression was performed in mice to evaluate atrial remodeling with atrial cell shortening assays, echocardiography, and AF inducibility with electrophysiology studies. RESULTS: In human patients with AF, PPP1R12C expression was increased 2-fold versus sinus rhythm controls (P=2.0×10-2; n=12 and 12 in each group) with >40% reduction in MLC2a phosphorylation (P=1.4×10-6; n=12 and 12 in each group). PPP1R12C-PP1c binding and PPP1R12C-MLC2a binding were significantly increased in AF (P=2.9×10-2 and 6.7×10-3, respectively; n=8 and 8 in each group). In vitro studies utilizing drug BDP5290, which inhibits T560-PPP1R12C phosphorylation, demonstrated increased PPP1R12C binding with both PP1c and MLC2a and dephosphorylation of MLC2a. Mice treated with lentiviral PPP1R12C vector demonstrated a 150% increase in left atrial size versus controls (P=5.0×10-6; n=12, 8, and 12), with reduced atrial strain and atrial ejection fraction. Pacing-induced AF in mice treated with lentiviral PPP1R12C vector was significantly higher than in controls (P=1.8×10-2 and 4.1×10-2, respectively; n=6, 6, and 5). CONCLUSIONS: Patients with AF exhibit increased levels of PPP1R12C protein compared with controls. PPP1R12C overexpression in mice increases PP1c targeting to MLC2a and causes MLC2a dephosphorylation, which reduces atrial contractility and increases AF inducibility. These findings suggest that PP1 regulation of sarcomere function at MLC2a is a key determinant of atrial contractility in AF.
AB - BACKGROUND: Atrial fibrillation (AF) - the most common sustained cardiac arrhythmia - increases thromboembolic stroke risk 5-fold. Although atrial hypocontractility contributes to stroke risk in AF, the molecular mechanisms reducing myofilament contractile function remain unknown. We tested the hypothesis that increased expression of PPP1R12C (protein phosphatase 1 regulatory subunit 12C) - the PP1 (protein phosphatase 1) regulatory subunit targeting MLC2a (atrial myosin light chain 2) - causes hypophosphorylation of MLC2a and results in atrial hypocontractility. METHODS: Right atrial appendage tissues were isolated from human patients with AF versus sinus rhythm controls. Western blots, coimmunoprecipitation, and phosphorylation studies were performed to examine how the PP1c (PP1 catalytic subunit)-PPP1R12C interaction causes MLC2a dephosphorylation. In vitro studies of pharmacological MRCK (myotonic dystrophy kinase-related Cdc42-binding kinase) inhibitor (BDP5290) in atrial HL-1 cells were performed to evaluate PP1 holoenzyme activity on MLC2a. Cardiac-specific lentiviral PPP1R12C overexpression was performed in mice to evaluate atrial remodeling with atrial cell shortening assays, echocardiography, and AF inducibility with electrophysiology studies. RESULTS: In human patients with AF, PPP1R12C expression was increased 2-fold versus sinus rhythm controls (P=2.0×10-2; n=12 and 12 in each group) with >40% reduction in MLC2a phosphorylation (P=1.4×10-6; n=12 and 12 in each group). PPP1R12C-PP1c binding and PPP1R12C-MLC2a binding were significantly increased in AF (P=2.9×10-2 and 6.7×10-3, respectively; n=8 and 8 in each group). In vitro studies utilizing drug BDP5290, which inhibits T560-PPP1R12C phosphorylation, demonstrated increased PPP1R12C binding with both PP1c and MLC2a and dephosphorylation of MLC2a. Mice treated with lentiviral PPP1R12C vector demonstrated a 150% increase in left atrial size versus controls (P=5.0×10-6; n=12, 8, and 12), with reduced atrial strain and atrial ejection fraction. Pacing-induced AF in mice treated with lentiviral PPP1R12C vector was significantly higher than in controls (P=1.8×10-2 and 4.1×10-2, respectively; n=6, 6, and 5). CONCLUSIONS: Patients with AF exhibit increased levels of PPP1R12C protein compared with controls. PPP1R12C overexpression in mice increases PP1c targeting to MLC2a and causes MLC2a dephosphorylation, which reduces atrial contractility and increases AF inducibility. These findings suggest that PP1 regulation of sarcomere function at MLC2a is a key determinant of atrial contractility in AF.
KW - arrhythmias, cardiac
KW - atrial fibrillation
KW - myosin light chains
KW - protein phosphatase 1
KW - stroke volume
UR - http://www.scopus.com/inward/record.url?scp=85174751784&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85174751784&partnerID=8YFLogxK
U2 - 10.1161/CIRCRESAHA.123.322516
DO - 10.1161/CIRCRESAHA.123.322516
M3 - Article
C2 - 37737016
AN - SCOPUS:85174751784
SN - 0009-7330
VL - 133
SP - 758
EP - 771
JO - Circulation research
JF - Circulation research
IS - 9
ER -