MAPT and Alzheimer disease: Here, we show that FcγRIIb is phosphorylated at tyrosine 273 by Aβ1-42 in neurons and in AD brains, and that this phosphorylation recruits SH2 domain-containing phosphatidylinositol 5′-phosphatase 2 (SHIP2, INPPL1) to increase PtdIns(3,4)P2 levels for tau hyperphosphorylation.