Molecular Mechanisms Controlling Actin Cytoskeleton Dynamics

Summary Actin exists in a dynamic equilibrium between monomeric (G-actin) and filamentous (F-actin) states, forming networks with distinct architectures such as filopodia, lamellipodia, focal adhesions, stress fibers, and muscle sarcomeres. The transition between G- and F-actin, along with the assembly, disassembly, and organization of F-actin networks, is regulated by hundreds of cytoskeletal proteins that specialize in various functions, including filament nucleation, elongation, severing, branching, and cross-linking. Despite significant progress, the molecular mechanisms governing the activities of many of these proteins remain poorly understood. This research program aims to address key knowledge gaps in four major areas: (a) Arp2/3 complex—how does each NPF-binding site contribute individually to Arp2/3 activation? Is coronin-7 an Arp2/3 complex inhibitor or a debrancher, and if so, what is the mechanism? How do factors such as nucleotide state, actin isoforms, and regulatory proteins influence branch stability and mechanosensation? (b) Filament dynamics at the barbed and pointed ends—how do CAP and AIP1 cooperate with cofilin to accelerate filament disassembly? What is the mechanism behind CARMIL- mediated barbed end uncapping? (c) Cytoskeletal mechanisms driving mitochondrial dynamics—what are the structural-functional mechanisms underlying MIRO-mediated recruitment of molecular motors and effectors (TRAK, Myo19, CENPF, and Parkin) to mitochondria? How does Myo19 function in this context? (d) Development of photoswitches targeting cytoskeletal components—how can structural biology and biochemistry be used to design next-generation photoswitches targeting actin cytoskeletal components with greater specificity and efficacy? This research builds on recent successes and expertise reflected in published and preparatory work. Project Number: 1R35GM161161-01 | Fiscal Year: 2026 | NIH Institute/Center: National Institute of General Medical Sciences (NIGMS) | Principal Investigator: ROBERTO DOMINGUEZ | Institution: UNIVERSITY OF PENNSYLVANIA, PHILADELPHIA, PA | Award Amount: $924,095 | Activity Code: R35 | Study Section: Special Emphasis Panel[ZRG1 MBBC-A (57)] View on NIH RePORTER: https://reporter.nih.gov/project-details/11257615