TY - JOUR T1 - Automatic sub-precision membrane contact site detection identifies convoluted tubular riboMERCs JF - bioRxiv DO - 10.1101/2022.06.23.497346 SP - 2022.06.23.497346 AU - Ben Cardoen AU - Guang Gao AU - Kurt R. Vandevoorde AU - Parsa Alan AU - William Liu AU - A. Wayne Vogl AU - Ghassan Hamarneh AU - Ivan R. Nabi Y1 - 2022/01/01 UR - http://biorxiv.org/content/early/2022/06/26/2022.06.23.497346.abstract N2 - The identification and morphological analysis of mitochondria-ER contacts (MERCs) by fluorescent microscopy is limited by sub-pixel resolution inter-organelle distances. Here, application of a novel Membrane Contact Site (MCS) detection algorithm, MCS-DETECT, to 3D STED super-resolution images reconstructs sub-resolution organelle interactions, identifying diverse MERCs. By EM, elongated ribosome-studded riboMERCs are present in HT-1080 but not COS-7 cells and, correspondingly, MCS-DETECT identifies extended large MERCs selectively in HT-1080. These are morphologically distinct from smaller smooth contacts in COS-7 cells and larger contacts induced in COS-7 cells by expression of an mitochondria-ER linker. Large ribo-MERC expression is reduced in Gp78 knockout HT-1080 cells and their induction by Gp78 in COS-7 cells is dependent on Gp78 ubiquitin ligase activity. Gp78-dependent riboMERCs present complex tubular shapes that intercalate between and contact multiple mitochondria. MCS-DETECT of whole cell super resolution 3D image volumes therefore identifies a novel convoluted tubular morphology for riboMERCs whose formation is dependent on Gp78 ubiquitin ligase activity.Competing Interest StatementThe authors have declared no competing interest. ER -