Role of microtubule-dependent transport in synaptic plasticity in hippocampal neurons

Resumen

The majority of excitatory synapses in the central nervous system are located at dendritic spines. These structures are considered key compartments for synaptic plasticity. During synaptic plasticity expression, spines alter their morphology and structure, and neurotransmitter receptor trafficking events take place. These phenomena have been related to actin cytoskeleton changes, but recently, microtubules (MT) have also been shown to modulate their own dynamics in an activity-dependent manner. Considering the close relationship between MT-dependent transport and endomembrane trafficking, and that between endomembrane trafficking and synaptic plasticity, we analyzed whether MT- dependent transport would play a role in modulating synaptic plasticity. Using a multidisciplinary approach that includes biochemistry, live confocal imaging, electrophysiology techniques and molecular biology for the development of new molecular tools, we have investigated the interaction of AMPA Receptors (AMPARs) with members of the kinesin family (KIF5, KIF17) and dynein during synaptic function. In particular, we have mapped-down the domains of these molecular motors that are required for the maintenance of basal transmission and for the allowance of synaptic plasticity expression in CA1 excitatory synapses from hippocampal slices. The data obtained suggested that the motor domain of KIF5 is not needed either for the maintenance of basal transmission or for the transport of GluA2 subunits along dendrites. However, its motor activity, as well as the motor activity of KIF17, seems to be crucial for long-term depression (LTD) to occur normally. Complementarily to these results, we have found that maintenance of basal transmission most likely depends on either regulatory domains of the neck-stalk region, or on interactions depending on the cargo binding domain of KIF5 and KIF17. Finally, we have also addressed whether minus-end transport, based on dynein, could modulate synaptic function. Our preliminary results indicate that dynein transport is not required for proper synaptic function. Our results suggest that MT-dependent transport is one of the many intracellular mechanisms finely tuning NMDAR-dependent LTD. Altogehter, this thesis shed some light into the interplay between cytoskeletal elements and the regulation of synaptic strength.