Biology subjects

Cretu, C.

Publications and source records attributed to Cretu, C..

2 recordsLinked to original sources

bioRxiv2025

Structure and function of otoferlin, a synaptic protein of sensory hair cells essential for hearing

Our sense of hearing relies upon speedy synaptic transmission of sound information from cochlear inner hair cells (IHCs) to spiral ganglion neurons (SGNs). To accomplish this, IHCs employ a sophisticated presynaptic machinery including the multi-C2-domain protein otoferlin which is affected by human deafness mutations. Otoferlin is essential for IHC-exocytosis but how it binds Ca2+ and the target membrane to serve synaptic vesicle (SV) tethering, docking and fusion remained unclear. Here, we obtained cryo-electron-microscopy structures of Ca2+-bound otoferlin and employed molecular dynamics simulations of membrane binding. We show that membrane binding involves C2B-C2G-domains and repositions C2F- and C2G-domains. Progressive disruption of Ca2+-binding by the C2D-domain in mice increasingly altered synaptic sound encoding and eliminated the Ca2+-cooperativity of SV-exocytosis, indicating that this Ca2+-cooperativity reflects binding of several Ca2+-ions to otoferlin. Together, our findings elucidate molecular mechanisms underlying otoferlin-mediated SV-docking and support a role of otoferlin as Ca2+-sensor of SV-fusion in IHCs.

neuroscience↗

bioRxiv2025

Structural Basis of Lipid Membrane Binding by Human Ferlins

Ferlins, ancient membrane proteins with a unique architecture, are central to multiple essential, Ca2+-dependent vesicle fusion processes. Despite numerous functional studies and their link to burdening human diseases, a mechanistic understanding of how these multi-C2 domain proteins interact with lipid membranes to promote their remodeling and fusion is currently lacking. Here, we elucidate the near-complete cryo-electron microscopy structures of human myoferlin and dysferlin in their Ca2+ and lipid-bound states. We show that ferlins adopt compact, ring-like tertiary structures achieved upon membrane binding. The top arch of the ferlin ring, comprising the C2C-C2D region, is rigid and varies little across the observed functional states. In contrast, the N-terminal C2B and the C-terminal C2F-C2G domains cycle between alternative conformations and, in response to Ca2+, close the ferlin ring, promoting tight interaction with the target membrane. Probing key domain interfaces validates the observed architecture and informs a model of how ferlins engage lipid bilayers in a Ca2+- dependent manner. This work reveals the general principles of human ferlin structures and provides a framework for future analyses of ferlin-dependent cellular functions and disease mechanisms.

biochemistry↗