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bioRxiv · 10.1101/2022.06.23.497346

Automatic sub-precision membrane contact site detection identifies convoluted tubular riboMERCs

Cardoen, B.·GAO, G.·Vandevoorde, K. R.·Alan, P.·Liu, W.·Vogl, A. W.·Hamarneh, G.·Nabi, I. R.
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Abstract

Identification and morphological analysis of mitochondria-ER contacts (MERCs) by fluorescent microscopy is limited by sub-pixel resolution inter-organelle distances. Application of a Membrane Contact Site (MCS) detection algorithm, MCS-DETECT, to 3D STED super-resolution image volumes reconstructs sub-resolution MERCs. MCS-DETECT shows that elongated ribosome-studded riboMERCs, present in HT-1080 but not COS-7 cells, are morphologically distinct from smaller smooth contacts and larger contacts induced by mitochondria-ER linker expression in COS-7 cells. riboMERC expression is reduced in Gp78 knockout HT-1080 cells and induced by Gp78 ubiquitin ligase activity in COS-7 cells. Knockdown of the riboMERC tether RRBP1 eliminates riboMERCs in both wild-type and Gp78 knockout HT-1080 cells. By MCS-DETECT, Gp78-dependent riboMERCs present complex tubular shapes that intercalate between and contact multiple mitochondria, that are lost upon RRBP1 knockdown. MCS-DETECT of 3D whole cell super-resolution image volumes therefore identifies a novel dual regulatory mechanism for tubular riboMERCs, whose formation is dependent on RRBP1 and size modulated by Gp78 E3 ubiquitin ligase activity. eTOC SummaryApplication of the sub-pixel resolution Membrane Contact Site (MCS) detection algorithm, MCS-DETECT, to 3D STED super-resolution image volumes identifies a novel dual regulatory mechanism for tubular riboMERCs, whose formation is dependent on RRBP1 and size modulated by Gp78 E3 ubiquitin ligase activity.

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Cardoen, B., GAO, G., Vandevoorde, K. R., Alan, P., Liu, W., Vogl, A. W., Hamarneh, G., Nabi, I. R.. 2022-06-26. Automatic sub-precision membrane contact site detection identifies convoluted tubular riboMERCs. https://doi.org/10.1101/2022.06.23.497346

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