Journal
JOURNAL OF BIOMEDICINE AND BIOTECHNOLOGY
Volume -, Issue -, Pages -Publisher
HINDAWI PUBLISHING CORPORATION
DOI: 10.1155/2010/727239
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Funding
- NIH [HL62881, T32 HL07249]
- AHA [0825748G]
- NATIONAL HEART, LUNG, AND BLOOD INSTITUTE [R01HL062881, T32HL007249] Funding Source: NIH RePORTER
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Titin, also known as connectin, is a large filamentous protein that greatly contributes to passive myocardial stiffness. In vitro evidence suggests that one of titin's spring elements, the PEVK, interacts with actin and that this adds a viscous component to passive stiffness. Differential splicing of titin gives rise to the stiff N2B and more compliant N2BA isoforms. Here we studied the titin-isoform dependence of titin-actin interaction and studied the bovine left atrium (BLA) that expresses mainly N2BA titin, and the bovine left ventricle (BLV) that expresses a mixture of both N2B and N2BA isforms. For comparison we also studied mouse left ventricular (MLV) myocardium which expresses predominately N2B titin. Using the actin-severing protein gelsolin, we obtained evidence that titin-actin interaction contributes significantly to passive myocardial stiffness in all tissue types, but most in MLV, least in BLA, and an intermediate level in BLV. We also studied whether titin-actin interaction is regulated by S100A1/calcium and found that calcium alone or S100A1 alone did not alter passive stiffness, but that combined they significantly lowered stiffness. We propose that titin-actin interaction is a viscous break that is on during diastole and off during systole.
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