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J Biol Chem. 2011 May 13;286(19):17060-8. doi: 10.1074/jbc.M110.197186. Epub 2011 Mar 14.

Identification of novel ryanodine receptor 1 (RyR1) protein interaction with calcium homeostasis endoplasmic reticulum protein (CHERP).

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Department of Physiology, University of Toronto, Ontario M5G 1L7, Canada.


The ryanodine receptor type 1 (RyR1) is a homotetrameric Ca(2+) release channel located in the sarcoplasmic reticulum of skeletal muscle where it plays a role in the initiation of skeletal muscle contraction. A soluble, 6×-histidine affinity-tagged cytosolic fragment of RyR1 (amino acids 1-4243) was expressed in HEK-293 cells, and metal affinity chromatography under native conditions was used to purify the peptide together with interacting proteins. When analyzed by gel-free liquid chromatography mass spectrometry (LC-MS), 703 proteins were identified under all conditions. This group of proteins was filtered to identify putative RyR interacting proteins by removing those proteins found in only 1 RyR purification and proteins for which average spectral counts were enriched by less than 4-fold over control values. This resulted in 49 potential RyR1 interacting proteins, and 4 were selected for additional interaction studies: calcium homeostasis endoplasmic reticulum protein (CHERP), endoplasmic reticulum-Golgi intermediate compartment 53-kDa protein (LMAN1), T-complex protein, and phosphorylase kinase. Western blotting showed that only CHERP co-purified with affinity-tagged RyR1 and was eluted with imidazole. Immunofluorescence showed that endogenous CHERP co-localizes with endogenous RyR1 in the sarcoplasmic reticulum of rat soleus muscle. A combination of overexpression of RyR1 in HEK-293 cells with siRNA-mediated suppression of CHERP showed that CHERP affects Ca(2+) release from the ER via RyR1. Thus, we propose that CHERP is an RyR1 interacting protein that may be involved in the regulation of excitation-contraction coupling.

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