A brain-enriched Drp1 isoform associates with lysosomes, late endosomes, and the plasma membrane.

Dynamin-related protein 1 (Drp1) constricts mitochondria as a mechanochemical GTPase during mitochondrial division. The Drp1 gene contains several alternative exons and produces multiple isoforms through RNA splicing. Here we performed a systematic analysis of Drp1 transcripts in different mouse tissues and identified a previously uncharacterized isoform that is highly enriched in the brain. This Drp1 isoform is termed Drp1ABCD because it contains four alterative exons: A, B, C, and D. Remarkably, Drp1ABCD is located at lysosomes, late endosomes, and the plasma membrane in addition to mitochondria. Furthermore, Drp1ABCD is concentrated at the interorganelle interface between mitochondria and lysosomes/late endosomes. The localizations of Drp1ABCD at lysosomes, late endosomes, and the plasma membrane require two exons, A and B, that are present in the GTPase domain. Drp1ABCD assembles onto these membranes in a manner that is regulated by its oligomerization and GTP hydrolysis. Experiments using lysosomal inhibitors show that the association of Drp1ABCD with lysosomes/late endosomes depends on lysosomal pH but not their protease activities. Thus, Drp1 may connect mitochondria to endosomal-lysosomal pathways in addition to mitochondrial division.

Coincident Phosphatidic Acid Interaction Restrains Drp1 in Mitochondrial Division.

Mitochondria divide to control their size, distribution, turnover, and function. Dynamin-related protein 1 (Drp1) is a critical mechanochemical GTPase that drives constriction during mitochondrial division. It is generally believed that mitochondrial division is regulated during recruitment of Drp1 to mitochondria and its oligomerization into a division apparatus. Here, we report an unforeseen mechanism that regulates mitochondrial division by coincident interactions of Drp1 with the head group and acyl chains of phospholipids. Drp1 recognizes the head group of phosphatidic acid (PA) and two saturated acyl chains of another phospholipid by penetrating into the hydrophobic core of the membrane. The dual phospholipid interactions restrain Drp1 via inhibition of oligomerization-stimulated GTP hydrolysis that promotes membrane constriction. Moreover, a PA-producing phospholipase, MitoPLD, binds Drp1, creating a PA-rich microenvironment in the vicinity of a division apparatus. Thus, PA controls the activation of Drp1 after the formation of the division apparatus.