HSPG2 and Alzheimer disease: The hydrolysis of PtdIns(4,5)P2 by phospholipase C (PLC) increases intracellular Ca2+, implicating familial AD mutations and suggesting that PLC inhibition could reduce Aβ42 secretion and Ca2+ entry (Landman et al., 2006; Yoo et al., 2000).