Published: 16 July, 2020 | Volume 5 - Issue 2 | Pages: 141-152
The normal adult heart is a well maintained machine that has a mechanism for growth replacement of the sarcomere that is lost by natural degeneration. This process ensures the heart has the strength of contraction to function correctly giving blood supply to the whole body. Some of the force of contraction of the sarcomere is transmitted to its major protein titin where its strength results in unfolding of a flexible section and release of a growth stimulant. The origin of all the cardiomyopathies can be traced to errors in this system resulting from mutations in a wide variety of the sarcomeric proteins. Too much or chronic tension transfer to titin giving increased growth resulting in hypertrophic cardiomyopathy (HCM) and too little leading to muscle wastage, dilated cardiomyopathy (DCM). HCM can ultimately lead to sudden cardiac death and DCM to heart failure. In this paper I show (1) a collection of the tension/ATPase calcium dependencies of cardiac myofibrils that define the mechanism of Ca2+ cooperativity. (2) I then reintroduce the stress/strain relationship to cardiomyopathies. (3) I then review the cardiomyopathy literature that contains similar Ca2+ dependency data to throw light on the mechanisms involved in generation of the types of myopathies from the mutations involved. In the review of cardiomyopathy there are two sections on mutations, the first dealing with those disrupting the Ca2+ cooperativity, i.e. the Hill coefficient of activation, leading to incomplete relaxation in diastole, chronic tension, and increased growth. Secondly dealing with those where the Ca2+ cooperativity is not affected giving either increased or decreased tension transfer to titin and changes in sarcomere growth.
Read Full Article HTML DOI: 10.29328/journal.jccm.1001101 Cite this Article Read Full Article PDF
Cardiac myosin binding cardiac protein-C (cMyBP-C); Cardiac troponin-I (cTnI); Cardiac troponin T (cTnT); Cardiac troponin C (cTnC); Calcium dependency; Magnesium ATP (MgATP); Myofilaments; ATPase; Contraction; Ca2+ cooperativity; Hill coefficient (nH); Sarcomere growth and loss
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