Abstract
Excitatory glutamatergic synapses at dendritic spines exchange and modulate their receptor content via lateral membrane diffusion. Several studies have shown that the thin spine neck impedes the access of membrane and solute molecules to the spine head. However, it is unclear whether the spine neck geometry alone restricts access to dendritic spines or if a physical barrier to the diffusion of molecules exists. Here, we investigated whether a complex of septin cytoskeletal GTPases localized at the base of the spine neck regulates diffusion across the spine neck. We found that, during development, a marker of the septin complex, Septin7 (Sept7), becomes localized to the spine neck where it forms a stable structure underneath the plasma membrane. We show that diffusion of receptors and bulk membrane, but not cytoplasmic proteins, is slower in spines bearing Sept7 at their neck. Finally, when Sept7 expression was suppressed by RNA interference, membrane molecules explored larger membrane areas. Our findings indicate that Sept7 regulates membrane protein access to spines.
MeSH terms
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Animals
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Cells, Cultured
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Dendritic Spines / metabolism*
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Diffusion
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Fluorescent Antibody Technique
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GTP Phosphohydrolases / metabolism
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Microscopy, Electron, Scanning
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Neurons / metabolism
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RNA Interference
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Rats
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Rats, Sprague-Dawley
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Septins / genetics
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Septins / metabolism*
Substances
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GTP Phosphohydrolases
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Septin7 protein, rat
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Septins
Grants and funding
H.E. was supported by a FEBS Long-Term Fellowship, T.T. by a Human Frontiers Short-Term Fellowship, and M.S. was an Investigator of the Howard Hughes Medical Institute. B.R. is supported by the Hungarian Scientific Research Fund Grant (OTKA K83830) and by the János Bólyai research fellowship by the Hungarian Academy of Sciences. D.C was supported by the CNRS and an ERC Advanced Grant. Morgan Sheng is an employee of Genentech, and Tomoko Tada is an employee of Otsuka Pharmaceutical, and both received funding in the form of salary from these companies. The electron microscopy of cultured neurons and confocal microscopy were done in the Bordeaux Imaging Center of the University of Bordeaux Segalen. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.