J Physiol Wellcome Trust-funded researchers
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

J Physiol Volume 586, Number 15, 3683-3700, August 1, 2008 DOI: 10.1113/jphysiol.2008.152181
This Article
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow All Versions of this Article:
586/15/3683    most recent
jphysiol.2008.152181v1
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Google Scholar
Right arrow Articles by Kreutziger, K. L.
Right arrow Articles by Regnier, M.
PubMed
Right arrow PubMed Citation
Right arrow Articles by Kreutziger, K. L.
Right arrow Articles by Regnier, M.
Related Collections
Right arrow Skeletal Muscle and Exercise

SKELETAL MUSCLE AND EXERCISE

Thin filament Ca2+ binding properties and regulatory unit interactions alter kinetics of tension development and relaxation in rabbit skeletal muscle

 Kareen L. Kreutziger1, Nicoletta Piroddi2, Beatrice Scellini2, Chiara Tesi2, Corrado Poggesi2 and Michael Regnier1

1 Department of Bioengineering, University of Washington, Seattle, WA 98195, USA
2 Dipartimento di Scienze Fisiologiche, Universitá degli Studi di Firenze, Florence, Italy

The influence of Ca2+ binding properties of individual troponin versus cooperative regulatory unit interactions along thin filaments on the rate tension develops and declines was examined in demembranated rabbit psoas fibres and isolated myofibrils. Native skeletal troponin C (sTnC) was replaced with sTnC mutants having altered Ca2+ dissociation rates (koff) or with mixtures of sTnC and D28A, D64A sTnC, that does not bind Ca2+ at sites I and II (xxsTnC), to reduce near-neighbour regulatory unit (RU) interactions. At saturating Ca2+, the rate of tension redevelopment (kTR) was not altered for fibres containing sTnC mutants with decreased koff or mixtures of sTnC:xxsTnC. We examined the influence of koff on maximal activation and relaxation in myofibrils because they allow rapid and large changes in [Ca2+]. In myofibrils with M80Q sTnCF27W (decreased koff), maximal tension, activation rate (kACT), kTR and rates of relaxation were not altered. With I60Q sTnCF27W (increased koff), maximal tension, kACT and kTR decreased, with no change in relaxation rates. Surprisingly, the duration of the slow phase of relaxation increased or decreased with decreased or increased koff, respectively. For all sTnC reconstitution conditions, Ca2+ dependence of kTR in fibres showed Ca2+ sensitivity of kTR (pCa50) shifted parallel to tension and low-Ca2+ kTR was elevated. Together the data suggest the Ca2+-dependent rate of tension development and the duration (but not rate) of relaxation can be greatly influenced by koff of sTnC. This influence of sTnC binding kinetics occurs primarily within individual RUs, with only minor contributions of RU interactions at low Ca2+.

(Received 5 February 2008; accepted after revision 3 June 2008; first published online 5 June 2008)
Corresponding author M. Regnier: Department of Bioengineering, University of Washington, Box 355061, Seattle, WA 98195, USA. Email: mregnier{at}u.washington.edu

Significant work was done in both laboratories.






HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
Copyright © 2008 The Physiological Society.