Effects of Phosphorylation on Drp1 Activation

Core Concepts

Phosphorylation at S579 and S600 alters Drp1 activity, impacting GTPase stimulation by various factors.

Abstract

Drp1, a GTPase essential for mitochondrial division, is regulated by phosphorylation at S579 and S600. Phospho-mimetic mutants show reduced oligomerization in the absence of GTP but still oligomerize with GTP. Both mutants exhibit decreased GTPase stimulation by actin filaments, cardiolipin, Mff, and MiD49. In vitro phosphorylation of S579 also results in similar effects. Interestingly, phosphorylated Drp1 on S579 inhibits actin-stimulated activity of wild-type Drp1. Additionally, the K38A mutant stimulates the GTPase activity of wild-type Drp1 under activating conditions. These findings suggest complex interactions between phosphorylation sites and activators in regulating Drp1 activity.

Stats

Phosphorylation at S579 and S600 impacts Drp1 activity. Both phospho-mimetic mutants display reduced oligomerization without GTP. Phosphorylated Drp1 on S579 inhibits actin-stimulated activity of wild-type Drp1. The K38A mutant stimulates the GTPase activity of wild-type Drp1 under activating conditions.

Quotes

"The most striking aspect of these results is that phosphorylation at the S579 site causes a decrease in activator-stimulated GTP hydrolysis." "Interestingly, actin still seems to synergize with Mff for activation of the phospho-mimetics." "These results suggest complex interactions between phosphorylation sites and activators in regulating Drp1 activity."

Key Insights Distilled From

Effects of phosphorylation on Drp1 activation by its receptors, actin, and cardiolipin

by Liu,A., Hatc... at www.biorxiv.org 08-20-2023

https://www.biorxiv.org/content/10.1101/2023.08.20.554022v1

Deeper Inquiries

How do different isoforms of Drp1 respond to phosphorylation at specific sites

Different isoforms of Drp1 respond differently to phosphorylation at specific sites. In the study, isoform 3 of Drp1 was predominantly used, which lacks alternately spliced exons near the S579 site. Phosphorylation at S579 in this isoform resulted in decreased activator-stimulated GTP hydrolysis activity. On the other hand, when using isoform 6 that contains all three splice inserts near the S579 site, similar attributes were observed with reduced stimulation by activators post-phosphorylation.

What additional factors might be involved in mediating the effects of phosphorylation on Drp1 activity

Several additional factors might be involved in mediating the effects of phosphorylation on Drp1 activity. One potential factor could be nucleotide diphosphate kinases (NDPKs) that catalyze GTP synthesis from GDP and ATP. These NDPKs could potentially increase local GTP concentration around Drp1, enhancing its GTPase activity post-phosphorylation. Additionally, interactions with other regulatory proteins or complexes may also play a role in modulating Drp1 activity after phosphorylation.

How can these findings be applied to understand mitochondrial fission regulation in cellular contexts

These findings can provide valuable insights into understanding mitochondrial fission regulation in cellular contexts. The study demonstrated that phosphorylation at specific sites on Drp1 can lead to alterations in its response to various activators like actin filaments and cardiolipin-containing vesicles. Understanding how these modifications impact Drp1 oligomerization and GTPase activation is crucial for unraveling the intricate mechanisms underlying mitochondrial fission regulation within cells. By elucidating these molecular pathways, researchers can gain a deeper understanding of how organelle dynamics are controlled and regulated during essential cellular processes such as division and maintenance of organelle integrity.