TY - JOUR
T1 - Drugging the Sarcomere, a Delicate Balance
T2 - Position of N-Terminal Charge of the Inhibitor W7
AU - Cai, Fangze
AU - Kampourakis, Thomas
AU - Cockburn, Kieran T.
AU - Sykes, Brian D.
N1 - Funding Information:
This study was supported by grants from the Heart and Stroke foundation of Canada (G-14-0005884 to B.D.S.), the University of Alberta Faculty of Medicine Transitional Program (B.D.S.), Motyl Graduate Studentship (F.C.), and British Heart Foundation (Fellowship FS/16/3/31887 to T.K.).
Publisher Copyright:
© 2022 American Chemical Society. All rights reserved.
PY - 2022/6/17
Y1 - 2022/6/17
N2 - W7 is a sarcomere inhibitor that decreases the calcium sensitivity of force development in cardiac muscle. W7 binds to the interface of the regulatory domain of cardiac troponin C (cNTnC) and the switch region of troponin I (cTnI), decreasing the binding of cTnI to cNTnC, presumably by electrostatic repulsion between the -NH3+ group of W7 and basic amino acids in cTnI. W7 analogs with a -CO2- tail are inactive. To evaluate the importance of the location of the charged -NH3+, we used a series of compounds W4, W6, W8, and W9, which have three less, one less, one more, and two more methylene groups in the tail region than W7. W6, W8, and W9 all bind tighter to cNTnC-cTnI chimera (cChimera) than W7, while W4 binds weaker. W4 and, strikingly, W6 have no effect on calcium sensitivity of force generation, while W8 and W9 decrease calcium sensitivity, but less than W7. The structures of the cChimera-W6 and cChimera-W8 complexes reveal that W6 and W8 bind to the same hydrophobic cleft as W7, with the aliphatic tail taking a similar route to the surface. NMR relaxation data show that internal flexibility in the tail of W7 is very limited. Alignment of the cChimera-W7 structure with the recent cryoEM structures of the cardiac sarcomere in the diastolic and systolic states reveals the critical location of the amino group. Small molecule induced structural changes can therefore affect the tightly balanced equilibrium between tethered components required for rapid contraction.
AB - W7 is a sarcomere inhibitor that decreases the calcium sensitivity of force development in cardiac muscle. W7 binds to the interface of the regulatory domain of cardiac troponin C (cNTnC) and the switch region of troponin I (cTnI), decreasing the binding of cTnI to cNTnC, presumably by electrostatic repulsion between the -NH3+ group of W7 and basic amino acids in cTnI. W7 analogs with a -CO2- tail are inactive. To evaluate the importance of the location of the charged -NH3+, we used a series of compounds W4, W6, W8, and W9, which have three less, one less, one more, and two more methylene groups in the tail region than W7. W6, W8, and W9 all bind tighter to cNTnC-cTnI chimera (cChimera) than W7, while W4 binds weaker. W4 and, strikingly, W6 have no effect on calcium sensitivity of force generation, while W8 and W9 decrease calcium sensitivity, but less than W7. The structures of the cChimera-W6 and cChimera-W8 complexes reveal that W6 and W8 bind to the same hydrophobic cleft as W7, with the aliphatic tail taking a similar route to the surface. NMR relaxation data show that internal flexibility in the tail of W7 is very limited. Alignment of the cChimera-W7 structure with the recent cryoEM structures of the cardiac sarcomere in the diastolic and systolic states reveals the critical location of the amino group. Small molecule induced structural changes can therefore affect the tightly balanced equilibrium between tethered components required for rapid contraction.
UR - http://www.scopus.com/inward/record.url?scp=85131967360&partnerID=8YFLogxK
U2 - 10.1021/acschembio.2c00126
DO - 10.1021/acschembio.2c00126
M3 - Article
C2 - 35649123
AN - SCOPUS:85131967360
SN - 1554-8929
VL - 17
SP - 1495
EP - 1504
JO - Acs Chemical Biology
JF - Acs Chemical Biology
IS - 6
ER -