Abstract
The mitochondria–ER–cortex anchor (MECA) forms a tripartite membrane contact site between mitochondria, the endoplasmic reticulum (ER), and the plasma membrane (PM). The core component of MECA, Num1, interacts with the PM and mitochondria via two distinct lipid-binding domains; however, the molecular mechanism by which Num1 interacts with the ER is unclear. Here, we demonstrate that Num1 contains a FFAT motif in its C-terminus that interacts with the integral ER membrane protein Scs2. While dispensable for Num1’s functions in mitochondrial tethering and dynein anchoring, the FFAT motif is required for Num1’s role in promoting mitochondrial division. Unexpectedly, we also reveal a novel function of MECA in regulating the distribution of phosphatidylinositol-4-phosphate (PI(4)P). Breaking Num1 association with any of the three membranes it tethers results in an accumulation of PI(4)P on the PM, likely via disrupting Sac1-mediated PI(4)P turnover. This work establishes MECA as an important regulatory hub that spatially organizes mitochondria, ER, and PM to coordinate crucial cellular functions.
| Original language | English (US) |
|---|---|
| Article number | e202308144 |
| Journal | Journal of Cell Biology |
| Volume | 223 |
| Issue number | 9 |
| DOIs | |
| State | Published - Sep 2 2024 |
Funding
We thank members of the Lackner lab for feedback on the manuscript and critical scientific discussions. We also thank Northwestern\u2019s Cell Biology Supergroup and the WignallLackner Cell Biology Group for constructive feedback on the project. Additional thanks to Jessica Hornick and Tong Zhang, who provided assistance with the fluorescence microscopy. The JFX650 dye (Grimm et al., 2021) used in the HaloTag imaging experiments was a kind gift from Luke Lavis at Janelia. All microscopy was performed at the Biological Imaging Facility at Northwestern University (RRID:SCR_017767), supported by the Chemistry for Life Processes Institute, the Northwestern University Office for Research, the Department of Molecular Biosciences, and the Rice Foundation. Proteomics services were performed by the Northwestern Proteomics Core Facility, generously supported by National Cancer Institute CCSG P30 CA060553 awarded to the Robert H. Lurie Comprehensive Cancer Center, instrumentation award (S10OD025194) from National Institutes of Health Office of Director, and the National Resource for Translational and Developmental Proteomics supported by P41 GM108569. J.C. Casler is supported by the National Institutes of Health and the National Institute of General Medical Sciences grant 1F32GM145160-01. C.S. Harper was supported by the National Institutes of Health Biotechnology Training Program 5T32GM008449-25 and the National Science Foundation Graduate Research Fellowship Program under Grant No. DGE-1842165. A.J. White was supported by the National Institutes of Health and the National Institute of General Medical Sciences grant T32 GM008382. H.L. Anderson was supported by the American Heart Association Predoctoral Fellowship 19PRE3481053. L.L. Lackner is supported by the National Institutes of Health and the National Institute of General Medical Sciences grant R01GM120303. Author contributions: J.C. Casler: Conceptualization, Data curation, Formal analysis, Funding acquisition, Investigation, Methodology, Project administration, Resources, Validation, Visualization, Writing - original draft, Writing - review & editing; C.S. Harper: Conceptualization, Investigation; A.J. White: Investigation; H.L. Anderson: Conceptualization; L.L. Lackner: Conceptualization, Funding acquisition, Methodology, Projectadministration, Resources, Supervision, Validation, Visualization, Writing - original draft, Writing - review & editing. All microscopy was performed at the Biological Imaging Facility at Northwestern University (RRID:SCR_017767), supported by the Chemistry for Life Processes Institute, the Northwestern University Office for Research, the Department of Molecular Biosciences, and the Rice Foundation. Proteomics services were performed by the Northwestern Proteomics Core Facility, generously supported by National Cancer Institute CCSG P30 CA060553 awarded to the Robert H. Lurie Comprehensive Cancer Center, instrumentation award (S10OD025194) from National Institutes of Health Office of Director, and the National Resource for Translational and Developmental Proteomics supported by P41 GM108569. J.C. Casler is supported by the National Institutes of Health and the National Institute of General Medical Sciences grant 1F32GM145160-01. C.S. Harper was supported by the National Institutes of Health Biotechnology Training Program 5T32GM008449-25 and the National Science Foundation Graduate Research Fellowship Program under Grant No. DGE-1842165. A.J. White was supported by the National Institutes of Health and the National Institute of General Medical Sciences grant T32 GM008382. H.L. Anderson was supported by the American Heart Association Predoctoral Fellowship 19PRE3481053. L.L. Lack-ner is supported by the National Institutes of Health and the National Institute of General Medical Sciences grant R01GM120303.
ASJC Scopus subject areas
- Cell Biology