Title

The role of skeletal troponin T in the regulation of skeletal muscle contraction

Date of Award

1998

Availability

Article

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Molecular and Cellular Pharmacology

First Committee Member

James Douglas Potter, Committee Chair

Abstract

Troponin T (TnT) is one of three proteins (including TnI and TnC) that form the troponin complex (Tn), which plays a critical role in the activation of the actomyosin ATPase responsible for the regulation of skeletal muscle contraction. Sequence analysis of the TnT gene predicts as many as 64 different isoforms, due to the presence of 6 alternatively spliced exons at the N-terminus and 2 mutually exclusively spliced exons at the C-terminus. Previous studies have suggested that the role of TnT in the regulation of contraction is to interact with and anchor the complex of TnI and TnC to actin-containing filaments through TnT's interaction with tropomyosin (Tm). I used two extremely powerful approaches, one using myofibrillar ATPase assays, and the other using skinned skeletal muscle fiber force development assays, to study the roles of these multiple TnT variants in the regulation of skeletal muscle contraction. My results suggest that, in addition to the role of anchoring the complex of TnT and TnC to actin containing filaments, TnT is critically involved in the regulation of actomyosin ATPase activation. I found evidence for the following steps in the regulation of skeletal muscle contraction by troponin T. First, the C-terminus of TnT interacts with TnC, and causes an activation of actomyosin ATPase activity. The Ca$\sp{2+}$-sensitivity of this activation depends on the C-terminus splice variants of TnT. Second, the N-terminal region of TnT, containing various alternatively spliced exons, appears to play a role in the level of activation of actomyosin ATPase activity once this interaction with TnC takes place. In summary, my results implicate the carboxy terminus alternatively spliced region of TnT in the regulation of actomyosin ATPase activation. Also I am providing some evidence that will lead to new insights into the role of N-terminus alternatively spliced region of TnT in the regulation of the level of activation of myofibrillar ATPase. These findings may explain the physiological significance of the multiple TnT variants.

Keywords

Biology, Molecular; Biology, Cell; Health Sciences, Pharmacology; Biology, Animal Physiology

Link to Full Text

http://access.library.miami.edu/login?url=http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:9905036