• An alternative pathway for membrane protein biogenesis at the endoplasmic reticulum

      O’Keefe, Sarah; orcid: 0000-0002-1744-0198; email: sarah.okeefe@manchester.ac.uk; Zong, Guanghui; orcid: 0000-0002-7335-039X; Duah, Kwabena B.; Andrews, Lauren E.; Shi, Wei Q.; orcid: 0000-0001-5453-1753; High, Stephen; orcid: 0000-0002-4532-8152; email: stephen.high@manchester.ac.uk (Nature Publishing Group UK, 2021-07-01)
      Abstract: The heterotrimeric Sec61 complex is a major site for the biogenesis of transmembrane proteins (TMPs), accepting nascent TMP precursors that are targeted to the endoplasmic reticulum (ER) by the signal recognition particle (SRP). Unlike most single-spanning membrane proteins, the integration of type III TMPs is completely resistant to small molecule inhibitors of the Sec61 translocon. Using siRNA-mediated depletion of specific ER components, in combination with the potent Sec61 inhibitor ipomoeassin F (Ipom-F), we show that type III TMPs utilise a distinct pathway for membrane integration at the ER. Hence, following SRP-mediated delivery to the ER, type III TMPs can uniquely access the membrane insertase activity of the ER membrane complex (EMC) via a mechanism that is facilitated by the Sec61 translocon. This alternative EMC-mediated insertion pathway allows type III TMPs to bypass the Ipom-F-mediated blockade of membrane integration that is seen with obligate Sec61 clients.
    • Ultraviolet light-induced collagen degradation inhibits melanoma invasion

      Budden, Timothy; Gaudy-Marqueste, Caroline; Porter, Andrew; orcid: 0000-0002-3353-7002; Kay, Emily; Gurung, Shilpa; Earnshaw, Charles H.; orcid: 0000-0002-7926-8506; Roeck, Katharina; Craig, Sarah; orcid: 0000-0003-1928-582X; Traves, Víctor; Krutmann, Jean; orcid: 0000-0001-8433-1517; et al. (Nature Publishing Group UK, 2021-05-12)
      Abstract: Ultraviolet radiation (UVR) damages the dermis and fibroblasts; and increases melanoma incidence. Fibroblasts and their matrix contribute to cancer, so we studied how UVR modifies dermal fibroblast function, the extracellular matrix (ECM) and melanoma invasion. We confirmed UVR-damaged fibroblasts persistently upregulate collagen-cleaving matrix metalloprotein-1 (MMP1) expression, reducing local collagen (COL1A1), and COL1A1 degradation by MMP1 decreased melanoma invasion. Conversely, inhibiting ECM degradation and MMP1 expression restored melanoma invasion. Primary cutaneous melanomas of aged humans show more cancer cells invade as single cells at the invasive front of melanomas expressing and depositing more collagen, and collagen and single melanoma cell invasion are robust predictors of poor melanoma-specific survival. Thus, primary melanomas arising over collagen-degraded skin are less invasive, and reduced invasion improves survival. However, melanoma-associated fibroblasts can restore invasion by increasing collagen synthesis. Finally, high COL1A1 gene expression is a biomarker of poor outcome across a range of primary cancers.