Role of RIM1α in short- and long-term synaptic plasticity at cerebellar parallel fibres.

The presynaptic terminals of synaptic connections are composed of a complex network of interacting proteins that collectively ensure proper synaptic transmission and plasticity characteristics. The key components of this network are the members of the RIM protein family. Here we show that RIM1α can influence short-term plasticity at cerebellar parallel-fibre synapses. We demonstrate that the loss of a single RIM isoform, RIM1α, leads to reduced calcium influx in cerebellar granule cell terminals, decreased release probability and consequently an enhanced short-term facilitation. In contrast, we find that presynaptic long-term plasticity is fully intact in the absence of RIM1α, arguing against its necessary role in the expression of this important process. Our data argue for a universal role of RIM1α in setting release probability via interaction with voltage-dependent calcium channels at different connections instead of synapse-specific functions.