Comprehensive binary interaction mapping of τ phosphotyrosine sites with SH2 domains in the human genome: Implications for the rational design of self-inhibitory phosphopeptides to target τ hyperphosphorylation signaling in Alzheimer's Disease

Human microtubule-associated protein Tau (tau) is abundant in the axons of neurons where it stabilizes microtubule bundles; abnormally hyperphosphorylated tau is a hallmark of Alzheimer's disease (AD) and related tauopathies. The hyperphosphorylation events can be recognized by phosphotyrosine-recognition domain SH2 (Src homology 2) to elicit downstream tau signaling in AD pathology. In this study, a comprehensive binary interaction map (CBIM) of all the 6 tau phosphotyrosine sites with 120 SH2 domains in the human genome was systematically created at structural level using computational analyses and binding assays, from which we were able to identify those of strong and moderate binding pairs of sites to domains. It is found that the SH2-recognition specificity of different tau phosphotyrosine sites has been evolutionally optimized to become roughly orthogonal to each other, and thus these site phosphorylations would regulate different but probably partially overlapped biological functions in tau signaling. Some SH2 groups such as SRC, RIN, PLCG, SOCS and SH2D were revealed to have effective binding potency as compared to others; they could be regarded as potential tau-associated proteins to transduce the downstream signaling. We further determined the systematic binding affinities of 6 tau-phosphopeptides to the 11 SH2 domains in SRC group, from which the FYN-tau(18) and YES -tau(29) pairs were identified as strong binders. Subsequently, rational molecular design was performed on tau(18) and tau(29) to derive a number of tau-phosphopeptide mutants with increased affinity; they are self-inhibitory candidates to competitively target tau hyperphosphorylation events in AD. In addition, it is revealed that the primary anchor pY(0) and secondary anchor X+3 of tau-phosphopeptides play an important role in SRC-group SH2 recognition, which confer stability and specificity to the SH2-phosphopeptide binding, respectively.