Plays a role in the regulation of the actin cytoskeleton through its interactions with actin capping protein (CP). May function to target CK2 to the plasma membrane thereby serving as an adapter to facilitate the phosphorylation of CP by protein kinase 2 (CK2). Appears to target ATM to the plasma membrane. Appears to also inhibit tumor cell growth by inhibiting AKT-mediated cell-survival. Also implicated in PI3K-regulated muscle differentiation, the regulation of AP-1 activity (plasma membrane bound AP-1 regulator that translocates to the nucleus) and the promotion of apoptosis induced by tumor necrosis factor TNF. When bound to PKB, it inhibits it probably by decreasing PKB level of phosphorylation. {ECO:0000269|PubMed:14729969, ECO:0000269|PubMed:15706351, ECO:0000269|PubMed:15831458, ECO:0000269|PubMed:16325375, ECO:0000269|PubMed:16987810, ECO:0000269|PubMed:17197158, ECO:0000269|PubMed:17942896}. This is the function of ENSG00000023902 (PLEKHO1, pleckstrin homology domain containing O1).