Organelle tethering by a homotypic PDZ interaction underlies formation of the Golgi membrane network.
Formation of the ribbon-like membrane network of the Golgi apparatus depends on GM130 and GRASP65, but the mechanism is unknown. We developed an in vivo organelle tethering assaying in which GRASP65 was targeted to the mitochondrial outer membrane either directly or via binding to GM130. Mitochondria bearing GRASP65 became tethered to one another, and this depended on a GRASP65 PDZ domain that was also required for GRASP65 self-interaction. Point mutation within the predicted binding groove of the GRASP65 PDZ domain blocked both tethering and, in a gene replacement assay, Golgi ribbon formation. Tethering also required proximate membrane anchoring of the PDZ domain, suggesting a mechanism that orientates the PDZ binding groove to favor interactions in trans. Thus, a homotypic PDZ interaction mediates organelle tethering in living cells.
Sengupta
Debrup
D
Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA 15213, USA.
Truschel
Steven
S
Bachert
Collin
C
Linstedt
Adam D
AD
D000595:Amino Acid Sequence; D001324:Autoantigens / Q000378:metabolism; D016000:Cluster Analysis; D006056:Golgi Apparatus / Q000378:metabolism*; D000077614:Golgi Matrix Proteins; D006367:HeLa Cells; D006801:Humans; D007425:Intracellular Membranes / Q000378:metabolism*; D008024:Ligands; D008565:Membrane Proteins / Q000737:chemistry* / Q000378:metabolism*; D008928:Mitochondria / Q000378:metabolism; D051336:Mitochondrial Membranes / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D054731:PDZ Domains; D055503:Protein Multimerization
D001324:Autoantigens; C108705:GORASP1 protein, human; D000077614:Golgi Matrix Proteins; C097741:Golgin subfamily A member 2; D008024:Ligands; D008565:Membrane Proteins