Distribution of Retention Signals to the Endoplasmic Reticulum in the Type 1 Ryanodine Receptor (Ca<SUP>2+</SUP> Release Channel)

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The ryanodine receptor type 1 (RyR1) is an intracellular calcium ion (Ca<SUP>2+</SUP>) release channel in the endoplasmic reticulum (ER) . Onefifth of the total 5, 037 amino acids of full-length RyR1 at the carboxyl (C) -terminus contains the transmembrane segments of the calcium ion channel, while the amino (N) -terminus is located in the cytoplasm and is referred to as the foot structure. In the present study the proposed structure of RyR1 was investigated by dividing the full-length cDNA of RyR1 into 11 cassettes (Csl-11) and expressing each cassette as a fusion protein with enhanced green fluorescent protein (EGFP) in Chinese hamster ovary (CHO) cells. Like full-length of RyR1, the C-terminal (4772 Asp to 5037 Ser), N-terminal (1st Met to 184 Thr encoded by Csl) and central regions (1743 Arg to 3224 Pro encoded by Cs5, 6 and 7) of RyRI remain in the cytoplasmic compartment following plasma membrane permeabilization. The remaining regions of RyR1, encoded by Cs2, 3, 4, 8, 9 and 10, leak out following membrane permeabiliza-tion. These results indicate the presence of at least four signaling sequences within the N-terminal, central or C-terminal regions of RyR1 responsible for ER retention.
昭和大学・昭和医学会の論文