Jaw1 is a protein found in the lumen of the endoplasmic reticulum (ER) and outer nuclear membrane, anchored by a C-terminal tail. Previously, Nishikawa and colleagues have shown that Jaw1 is important for Ca2+ release from the ER and for maintaining nuclear shape. Additionally, it has previously been shown that the C-terminal tail of Jaw1 can be partially cleaved, and thus Jaw1 exists in both cleaved and uncleaved forms. However, the functional significance of this cleavage is unclear. Now, this study (Kozono et al., 2023) sheds light on this question, demonstrating that the C-terminal region of Jaw1 is cleaved after its insertion into the ER by the signal peptidase complex (SPC). Specifically, the authors find that this cleavage requires the catalytic subunit SEC11A, but not SEC11C, of the SPC. Using a cleavage-deficient mutant of the SPC, they show that loss of Jaw1 cleavage reduces the ability of inositol 1,4,5-trisphosphate receptors (IP3Rs) to release Ca2+ from the ER. The nuclear shape appears unperturbed, however, suggesting that the cleavage of Jaw1 is specifically required for its functions in the ER. In conclusion, this paper elucidates the mechanism and function of Jaw1 cleavage and, thus, how its functions in the ER and nuclear membrane are differentially regulated by the SPC.
In the Jaw1 of the ER: a tail of cleavage
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In the Jaw1 of the ER: a tail of cleavage. J Cell Sci 15 February 2023; 136 (4): e136_e0402. doi:
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