Exon Inclusion Modulates Conformational Plasticity and Autoinhibition of the Intersectin 1 SH3A Domain
Gerth, Fabian and Jäpel, Maria and Sticht, Jana and Kuropka, Benno and Schmitt, Xiao Jakob and Driller, Jan H. and Loll, Bernhard, Wahl, Markus C. and Pagel, Kevin and Haucke, Volker and Freund, Christian – 2019
The scaffolding protein intersectin 1 plays important roles in clathrin-mediated endocytosis and in the replenishment of release-ready synaptic vesicles (SV). Two splice variants of intersectin's SH3A domain are expressed in the brain, and association of the neuron-specific variant with synapsin I has been shown to enable sustained neurotransmission and to be regulated by an adjacent C-terminal motif. Here, we demonstrate that the ubiquitously expressed short SH3A variant of intersectin 1 interacts with an N-terminal intramolecular sequence that operates synergistically with the C-terminal motif. NMR spectroscopic investigations show that the five-amino acid insertion into the ? strand 2 of the neuronal SH3A variant introduces conformational plasticity incompatible with binding of the N-terminal sequence. The difference in the autoregulatory mechanism of the domain's variants differentially affects its synaptic binding partners, thereby establishing alternative splicing in conjunction with autoinhibitory motif variation as a mechanism to regulate protein interaction networks.