ER residency of the ceramide phosphoethanolamine synthase SMSr relies on homotypic oligomerization mediated by its SAM domain
Autor(en): | Cabukusta, Birol Kol, Matthijs Kneller, Laura Hilderink, Angelika Bickert, Andreas Mina, John G. M. Korneev, Sergei Holthuis, Joost C. M. |
Stichwörter: | ALPHA-MOTIF DOMAIN; APOPTOSIS; CANCER-CELLS; CURCUMIN; DIACYLGLYCEROL KINASE-DELTA; ENDOPLASMIC-RETICULUM; Multidisciplinary Sciences; PROTEIN SMSR; REGULATED OLIGOMERIZATION; Science & Technology - Other Topics; SPHINGOLIPID BIOSYNTHESIS; SPHINGOMYELIN SYNTHASES | Erscheinungsdatum: | 2017 | Herausgeber: | NATURE PUBLISHING GROUP | Journal: | SCIENTIFIC REPORTS | Volumen: | 7 | Zusammenfassung: | SMSr/SAMD8 is an ER-resident ceramide phosphoethanolamine synthase with a critical role in controlling ER ceramides and suppressing ceramide-induced apoptosis in cultured cells. SMSr-mediated ceramide homeostasis relies on the enzyme's catalytic activity as well as on its N-terminal sterile alpha-motif or SAM domain. Here we report that SMSr-SAM is structurally and functionally related to the SAM domain of diacylglycerol kinase DGKd, a central regulator of lipid signaling at the plasma membrane. Native gel electrophoresis indicates that both SAM domains form homotypic oligomers. Chemical crosslinking studies show that SMSr self-associates into ER-resident trimers and hexamers that resemble the helical oligomers formed by DGKd-SAM. Residues critical for DGKd-SAM oligomerization are conserved in SMSr-SAM and their substitution causes a dissociation of SMSr oligomers as well as a partial redistribution of the enzyme to the Golgi. Conversely, treatment of cells with curcumin, a drug disrupting ceramide and Ca2+ homeostasis in the ER, stabilizes SMSr oligomers and promotes retention of the enzyme in the ER. Our data provide first demonstration of a multi-pass membrane protein that undergoes homotypic oligomerization via its SAM domain and indicate that SAM-mediated self-assembly of SMSr is required for efficient retention of the enzyme in the ER. |
ISSN: | 20452322 | DOI: | 10.1038/srep41290 |
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