1. Fluorescence approaches to the study of the actin-nucleating and bundling activities of synapsin I
- Author
-
F. Grohovaz, Fabio Benfenati, P.E. Ceccaldi, Evelina Chieregatti, Flavia Valtorta, Riccardo Fesce, Valtorta, Flavia, Ceccaldi, Pe, Grohovaz, Fabio, Chieregatti, E, Fesce, R, and Benfenati, F.
- Subjects
Synapsin I ,Microscopy ,Polymers ,General Neuroscience ,macromolecular substances ,Synapsin ,Biology ,Microfilament ,Fluoresceins ,Synapsins ,Synaptic vesicle ,Actins ,Cell biology ,nervous system ,Physiology (medical) ,Phosphoprotein ,Fluorescence microscope ,Animals ,Cattle ,Fluorescein ,Fluorometry ,Television ,Cytoskeleton ,Actin - Abstract
Synapsin I is a neuron-specific phosphoprotein which binds to small synaptic vesicles and actin in a phosphorylation-dependent fashion. We have analyzed the ability of synapsin I to interact with actin monomers and filaments using purified proteins derivatized with fluorescent probes. Synapsin I accelerates the initial rate of actin polymerization and increases the final steady-state levels of polymerized actin. The fraction of total actin polymerized by synapsin I strongly depends on the synapsin I-actin ratio. We have visualized the actin-bundling activity of synapsin I using a non-perturbing method, video-enhanced microscopy of fluoresceinated synapsin I and actin filaments. Our findings suggest that synapsin I exerts a control on the physical characteristics of the cytoskeletal network of the nerve terminal and are consistent with the proposed role of synapsin I in mediating the interaction of synaptic vesicles with actin.
- Published
- 1993