Researchers are exploring whether these ubiquitous fluorinated molecules might worsen infections or hamper vaccine effectiveness.
Image credit: Shutterstock/Dmitry Naumov.
Edited by Thomas C. Südhof, Stanford University School of Medicine, Stanford, CA, and approved August 15, 2016 (received for review March 31, 2016)
Significance
Highly regulated and precise positioning of Ca2+ channels at the active zone (AZ) controls Ca2+ nanodomains at release sites. Their exact localization affects vesicular release probability (PVR) and is important for proper synaptic transmission during repetitive stimulation. We provide a detailed analysis of synaptic transmission combined with superresolution imaging of the AZ organization in mouse hippocampal synapses lacking Rab-interacting molecule-binding protein 2 (RIM-BP2). By dual- and triple-channel time-gated stimulated emission depletion (gSTED) microscopy, we directly show that RIM-BP2 fine-tunes voltage-gated Ca2+ channel 2.1 (CaV2.1) localization at the AZ. We reveal that RIM-BP2 likely regulates the Ca2+ nanodomain by positioning CaV2.1 channels close to synaptic vesicle release sites. Loss of RIM-BP2 reduces PVR and alters short-term plasticity.
Abstract
The tight spatial coupling of synaptic vesicles and voltage-gated Ca2+ channels (CaVs) ensures efficient action potential-triggered neurotransmitter release from presynaptic active zones (AZs). Rab-interacting molecule-binding proteins (RIM-BPs) interact with Ca2+ channels and via RIM with other components of the release machinery. Although human RIM-BPs have been implicated in autism spectrum disorders, little is known about the role of mammalian RIM-BPs in synaptic transmission. We investigated RIM-BP2–deficient murine hippocampal neurons in cultures and slices. Short-term facilitation is significantly enhanced in both model systems. Detailed analysis in culture revealed a reduction in initial release probability, which presumably underlies the increased short-term facilitation. Superresolution microscopy revealed an impairment in CaV2.1 clustering at AZs, which likely alters Ca2+ nanodomains at release sites and thereby affects release probability. Additional deletion of RIM-BP1 does not exacerbate the phenotype, indicating that RIM-BP2 is the dominating RIM-BP isoform at these synapses.
Footnotes
↵1M.K.G., M.M., and S.R.-A. contributed equally to this work.
- ↵2To whom correspondence may be addressed. Email: christian.rosenmund{at}charite.de, dietmar.schmitz{at}charite.de, or stephan.sigrist{at}fu-berlin.de.
Author contributions: M.K.G., M.M., S.R.-A., B.J.E., V.H., D.S., S.J.S., and C.R. designed research; M.K.G., M.M., S.R.-A., C.G.W., M.M.B., T.T., T.R., M.P., G.V., A.S., and B.R.R. performed research; A.M.W. contributed new reagents/analytic tools; M.K.G., M.M., S.R.-A., C.G.W., M.M.B., T.T., T.R., M.P., and B.R.R. analyzed data; A.M.W. provided data discussion; and M.K.G., M.M., S.R.-A., V.H., D.S., S.J.S., and C.R. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1605256113/-/DCSupplemental.
Freely available online through the PNAS open access option.
RIM-BP2 sets release probability at mouse synapses
Article Classifications
- Biological Sciences
- Neuroscience
Sign up for Article Alerts
Jump to section
You May Also be Interested in
Recent experiments and simulations are starting to answer some fundamental questions about how life came to be.
Image credit: Shutterstock/Radoslaw Lecyk.
Archaeologists have long tried to define the transition between the two time periods.
Image credit: Ceri Shipton.
Jonathon Yuly, David Beratan, and Peng Zhang investigate how electron bifurcation reactions work.
A study finds that giant pandas roll in horse manure to increase their cold tolerance.
Image credit: Fuwen Wei.