Abstract 20419: Citrullination in Actin-Tropomyosin-Myosin Complex: Novel Regulatory Mechanism
Background: A novel protein post-translational modification, citrullination was shown previously in a number of key myofilament proteins, tropomyosin (R 133, R 238), actin (R 39) and myosin heavy chain (R 1176, 1303, 1434) in HF patient (values for total spectra counts for citrullinated proteins in control, ISHD and IDCM: 1.8 ±1.3, 3.2±2.7 and 2.3±1.9, respectively). The alterations in contractile proteins underlying enhanced Ca2+-sensitivity of the contractile apparatus in end-stage failing human myocardium are still not resolved. Protein citrullination arises from the enzymatic conversion of arginine residues to citrulline result in loss of a positive charge and reduction in hydrogen-bonding ability. And here, the biophysical and biochemical effect on myofilament function is determined.
Method: F-actin-tropomyosin binding, tropomyosin-actin-myosin, actin-myosin and myosin ATPase activity assays, and F-actin stability assays were carried out.
Results: In vitro citrullinated tropomyosin significantly enhance affinity for F-actin (p=0.001) and decrease in the ATPase activity (p=0.06). Furthermore, citrullination of myosin HMM is not essential for actin affinity, although it modulate ATPase activation (p=0.3). Contrary, the ATPase activity is increase by pretreatment of actin (but not myosin) with PAD2 (p=0.09).
Conclusion: Citrullination of the contractile proteins could affect different aspects of regulatory function. It either triggers a structural change or stabilizes a conformation that is necessary for actin-activated release of Pi and completion of the ATPase cycle.
Significance: Citrullination of specific myofilament proteins in HF can have dramatic effect on modulating actin filament integrity and myosin function and tropomyosin action on myofilament regulation.
Author Disclosures: J. Fert-Bober: None. J. Van Eyk: None.
- © 2014 by American Heart Association, Inc.