Cyclic AMP-dependent Protein Kinase Phosphorylation of Drp1 Regulates Its GTPase Activity and Mitochondrial Morphology

TLDR

Mitochondrial dynamics depend on the dynamin-like GTPase Drp1, whose domain interactions drive assembly and GTPase activity, yet the regulatory mechanisms controlling Drp1 remain poorly understood. The authors show that cAMP‑dependent protein kinase phosphorylates Drp1 at Ser637 in the GED domain, reducing intramolecular GTP‑binding/middle domain interactions and thereby lowering GTPase activity. Phosphorylation of Drp1 at Ser637 suppresses its GTPase activity, disrupts intramolecular domain interactions, and markedly reduces mitochondrial fission, leading to altered mitochondrial morphology.

Abstract

Mitochondria in cells comprise a tubulovesicular reticulum shaped by dynamic fission and fusion events. The multimeric dynamin-like GTPase Drp1 is a critical protein mediating mitochondrial division. It harbors multiple motifs including GTP-binding, middle, and GTPase effector (GED) domains that are important for both intramolecular and intermolecular interactions. As for other members of the dynamin superfamily, such interactions are critical for assembly of higher-order structures and cooperative increases in GTPase activity. Although the functions of Drp1 in cells have been extensively studied, mechanisms underlying its regulation remain less clear. Here, we have identified cAMP-dependent protein kinase-dependent phosphorylation of Drp1 within the GED domain at Ser(637) that inhibits Drp1 GTPase activity. Mechanistically, this change in GTPase activity likely derives from decreased interaction of GTP-binding/middle domains with the GED domain since the phosphomimetic S637D mutation impairs this intramolecular interaction but not Drp1-Drp1 intermolecular interactions. Using the phosphomimetic S637D substitution, we also demonstrate that mitochondrial fission is prominently inhibited in cells. Thus, protein phosphorylation at Ser(637) results in clear alterations in Drp1 function and mitochondrial morphology that are likely involved in dynamic regulation of mitochondrial division in cells.