Myoplasmic resting Ca2{+} regulation by RyR is under control of a novel Ca2{+}-binding region of the ryanodine receptor

Passive SR Ca2+-leak through the ryanodine receptor (RyR) plays a critical role in the mechanisms that regulate intracellular resting Ca2+ concentration ([Ca2+]rest) in muscle. This process appears to be isoform specific as expression of either RyR1 or RyR3 confers myotubes with different [Ca2+]rest. Using chimeric RyR3/RyR1 receptors expressed in dyspedic myotubes here we show that isoform dependent regulation of [Ca2+]rest is primarily defined by a small region of the receptor encompassing amino acid 3770-4007 of RyR1 (3620-3859 of RyR3) named as the Ca2+ Leak Regulatory (CLR) region.[Ca2+]rest regulation by the CLR region was associated with alteration of RyRs Ca2+-activation profile and changes in SR Ca2+-leak rates. Biochemical analysis using Tb3+ binding assays and intrinsic tryptophan fluorescence spectroscopy of purified CLR domains revealed that this determinant of RyRs holds a novel Ca2+-binding domain with conformational properties that are distinctive of each isoform. Our data suggest that the CLR region provide channels with unique functional properties that modulate the rate of passive SR Ca2+-leak and confer RyR1 and RyR3 with distinctive [Ca2+]restregulatory properties. The identification of a new Ca2+-binding domain of RyRs with a key modulatory role in [Ca2+]restregulation provides new insights into Ca2+-mediated regulation of RyRs.

Source: BJ Signal - March 18, 2014 Category: Biochemistry Authors: Y Chen, S Xue, J Zou, J R Lopez, J J Yang, C F Perez Tags: BJ ChemBio Source Type: research