Role of RIN1 in shaping structural and functional properties of hippocampal synapses

The strength of excitatory synapses is regulated through structural and functional changes, but how they are coordinated at the molecular level is incompletely understood. Ras and Rab interactor protein 1 (RIN1) is a Ras effector protein, that is highly expressed in forebrain excitatory neurons, and loss of RIN1 has been shown to affect synaptic plasticity and learning. Our previous work demonstrated that RIN1 destabilizes synapses and supports postsynaptic AMPA receptor endocytosis during chemical long-term depression. As RIN1 plays a role in enhancing signaling of the tyrosine kinases Abl and Arg which regulate actin cytoskeletal remodeling, and in activation of the small GTPase Rab5 which promotes receptor endocytosis, we hypothesized that this dual function of RIN1 could orchestrate AMPA receptor trafficking and spine structural changes.To address this question, we generated several RIN1 mutants to impair distinct protein functions and characterized them in biochemical assays. We then re-express wild-type RIN1 and RIN1 loss- or gain-of-function mutants in hippocampal cultures obtained from RIN1-knockout mice to assess their impact on spine morphology and synaptic transmission. Our current results suggest differential effects on spine density and morphology of these RIN1 mutants. In ongoing experiments, we also characterize their functional impact on aspects of excitatory synaptic transmission and plasticity.