Surface Traffic in Synaptic Membranes
The precision of signal transmission in chemical synapses is highly dependent on the structural alignment between pre- and postsynaptic components. The thermal agitation of transmembrane signaling molecules by surrounding lipid molecules and activity-driv
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Surface Traffic in Synaptic Membranes Martin Heine
Abstract The precision of signal transmission in chemical synapses is highly dependent on the structural alignment between pre- and postsynaptic components. The thermal agitation of transmembrane signaling molecules by surrounding lipid molecules and activity-driven changes in the local protein interaction affinities indicate a dynamic molecular traffic of molecules within synapses. The observation of local protein surface dynamics starts to be a useful tool to determine the contribution of intracellular and extracellular structures in organizing a plastic synapse. Local rearrangements by lateral diffusion in the synaptic and perisynaptic membrane induce fast density changes of signaling molecules and enable the synapse to change efficacy in short time scales. The degree of lateral mobility is restricted by many passive and active interactions inside and outside the membrane. AMPAR at the glutamatergic synapse are the best explored receptors in this respect and reviewed here as an example molecule. In addition, transsynaptic adhesion molecule complexes also appear highly dynamically in the synapse and do further support the importance of local surface traffic in subcellular compartments like synapses. Keywords AMPA-receptors • Endocytosis • Exocytosis • Lateral diffusion • Quantum dots
M. Heine (*) Research Group Molecular Physiology, Leibniz Institute for Neurobiology, 39118 Magdeburg, Germany e-mail: [email protected] M.R. Kreutz and C. Sala (eds.), Synaptic Plasticity, Advances in Experimental Medicine and Biology 970, DOI 10.1007/978-3-7091-0932-8_9, # Springer-Verlag/Wien 2012
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Introduction
The local number, composition, and density of signaling molecules at synapses are important determinants of synaptic plasticity. Changes in synaptic protein content were identified to be basic features of synaptic plasticity and memory formation (Kessels and Malinow 2009). Mechanisms like the endo-exocytotic cycle of synaptic membrane proteins, intracellular transport, and local synthesis of new molecules were shown to change local number, density, and composition of proteins within a time window of minutes to hours (Newpher and Ehlers 2008). Initialization of short- and long-term changes in synaptic plasticity takes place in a few milliseconds and is known to depend on interplay between pre- and postsynaptic mechanisms. Kinetic properties of pre- and postsynaptic molecules are identified to play a major role within this very first moment of activity changes, including calcium-induced facilitation or depression of presynaptic release properties (Catterall and Few 2008; Neher and Sakaba 2008) or postsynaptic receptor saturation and desensitization (Trussell et al. 1993; Xu-Friedman and Regehr 2003). In order to weaken or strengthen synaptic transmission, the alignment between pre- and postsynaptic elements has been shown to be crucial (Franks et al. 2003; Raghavachari and Lisman 2004; Shouval 2005; Xie et al. 1997). In this respect, t
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