Helyszín: Elméleti Orvostudományi Központ, Budapest 1094 Budapest, Tűzoltó utca 37-47.
a Biofizikai és Sugárbiológiai Intézet
Egyetemi Oktatási Központ, 1094 Budapest,
Tűzoltó u. 37-47., Beznák Aladár terem
2017. december 7-én
11:00 órai kezdettel
Dr Dilson Rassier
Muscle Physiology and Biophysics Laboratory,
McGill University, Montreál, Kanada
The mechanisms behind the load
dependence of force produced by myosin
filaments, sarcomeres and myofibrils
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Az előadás kivonata:
The mechanisms behind the load dependence of force produced by myosin filaments, sarcomeres and myofibrils. During myofibril activation, sarcomeres develop forces that are balanced through a complex, dynamic interaction among their contractile and elastic structures. The force is dependent on the length of the sarcomeres and the external load imposed to the myofibril. The mechanisms that regulate this load-dependent force and its connection with inter-sarcomere dynamics are unclear, but can be associated with myosin-actin interactions and/or the properties of titin molecules. In order to understand the underlying mechanisms, we developed (i) a system with microfluidic perfusion to point-activate/deactivate one half-sarcomere/sarcomere within a myofibril, (ii) a system to measure the mechanical properties of mechanically isolated sarcomeres and half-sarcomeres, and (iii) a system to measure the load-dependent force produced to individual myosin filaments while interacting with actin. We found that while the force developed by an isolated half-sarcomere or sarcomere can be predicted by their degree of overlap between myosin and actin filaments, and a Ca2+-dependent stiffness of titin, the force produced by myofibrils is more complex, and also depends on half-sarcomere length non-uniformity, which is regulated by the cooperative work of the contractile and elastic elements within a myofibril. Finally, we observed that the work produced by myosin filaments can explain the transient load dependence of force, but cannot explain the residual changes in force observed after loads are imposed to the contractile system. ontractile and elastic elements within a myofibril. Finally, we observed that the work produced by myosin filaments can explain the transient load dependence of force, but cannot explain the residual changes in force observed after loads are imposed to the contractile system.