Biology subjects

Nolden, K. A.

Publications and source records attributed to Nolden, K. A..

2 recordsLinked to original sources

bioRxiv2025

Drp1 Proteins Released from Hydrolysis-driven Scaffold Disassembly Trigger Nucleotide-dependent Membrane Remodeling to Promote Scission

Dynamin-related protein (Drp1) drives mitochondrial fission, dysregulation of which leads to neurodegenerative, metabolic, and apoptotic disorders. The precise mechanism of fission completion is unclear. One prevailing model is based on GTP-driven assembly of Drp1 helices that increase confinement via force generation. However, constriction to nanoscopic tubule radii appears necessary but not sufficient for scission. The other is based on GTP-driven disassembly of a constricting Drp1 scaffold that drives a membrane disturbance, but the relation of disassembly to scission and GTP hydrolysis remain uncertain. Elucidation of mitochondrial fission is complicated by the multiple time-involved in the dynamics of mechanoenzyme activity, oligomer disassembly, and membrane remodeling. Using machine learning, synchrotron x-ray scattering, and a theoretical model, our data support a model where progressive GTP hydrolysis enable free Drp1s to increase their capacity for inducing membrane negative Gaussian curvature (NGC). Furthermore, we identify and Drp1 variants that diminish this progressive capacity. Machine learning reveals that predicted NGC-generating sequences of the Drp1 oligomer are not in contact with the confined lipid tube, that scission-enhancing membrane remodeling is triggered by free Drp1 released upon disassembly. TeaserFree Drp1 released from disassembly of oligomeric Drp1 constrictase promotes GTP-hydrolysis dependent mitochondrial scission.

biophysics↗

bioRxiv2023

Human Fis1 directly interacts with Drp1 in an evolutionarily conserved manner to promote mitochondrial fission

Mitochondrial Fission Protein 1 (Fis1) and Dynamin Related Protein 1 (Drp1) are the only two proteins evolutionarily conserved for mitochondrial fission, and directly interact in S. cerevisiae to facilitate membrane scission. However, it remains unclear if a direct interaction is conserved in higher eukaryotes as other Drp1 recruiters, not present in yeast, are known. Using NMR, differential scanning fluorimetry, and microscale thermophoresis, we determined that human Fis1 directly interacts with human Drp1 (KD = 12-68 {micro}M), and appears to prevent Drp1 assembly, but not GTP hydrolysis. Similar to yeast, the Fis1-Drp1 interaction appears governed by two structural features of Fis1: its N-terminal arm and a conserved surface. Alanine scanning mutagenesis of the arm identified both loss- and gain-of-function alleles with mitochondrial morphologies ranging from highly elongated (N6A) to highly fragmented (E7A) demonstrating a profound ability of Fis1 to govern morphology in human cells. An integrated analysis identified a conserved Fis1 residue, Y76, that upon substitution to alanine, but not phenylalanine, also caused highly fragmented mitochondria. The similar phenotypic effects of the E7A and Y76A substitutions, along with NMR data, support that intramolecular interactions occur between the arm and a conserved surface on Fis1 to promote Drp1-mediated fission as in S. cerevisiae. These findings indicate that some aspects of Drp1-mediated fission in humans derive from direct Fis1-Drp1 interactions that are conserved across eukaryotes.

biochemistry↗