GIT2 is dispensable for normal learning and memory function due to a predominant brain GIT2 splice variant that evades GIT/PIX complexes

Abstract

32 33 G protein-coupled receptor kinase-interacting protein 2 (GIT2) and GIT1 are highly similar, sharing 34 the same domain structure and many binding partners. The most important GIT partners are the 35 p21-activated protein kinase-interacting exchange factor (PIX) proteins, since through homomeric 36 and heteromeric interactions, GIT and PIX proteins form oligomeric GIT/PIX complexes. Oligomeric 37 GIT/PIX complexes function both as regulators of small GTP-binding proteins and as scaffolds for 38 signalling molecules, including p21-activated protein kinases (PAKs). Deficits in learning and 39 memory have been demonstrated in GIT1 knockout mice, and it has been assumed that GIT2 also 40 would affect learning and memory. Unexpectedly, we find that GIT2-deficient mice respond 41 normally in multiple tests of learning and memory, and have normal hippocampal long-term 42 potentiation. Further, we find no evidence that GIT2 regulates ADHD-like phenotypes. To 43 investigate why GIT2 and GIT1 differ so markedly in the brain, we identified the major isoform of 44 GIT2 in the brain as a previously uncharacterized splice variant, GIT2(DBCE). This variant cannot 45 dimerize or form oligomeric complexes with PIX proteins, and is thus incapable of regulating PAK 46 in synapses, compared to oligomeric GIT1/PIX complexes. Because localized activation of PAK in 47 synapses is required for structural plasticity underlying cognitive performance, loss of monomeric 48 GIT2(DBCE) in the brain does not influence these responses. 49 50 Methods 109 110 Plasmids 111