Essential regulator of neutrophil polarity. Regulates neutrophil polarization by regulating AKT1 phosphorylation through a mechanism that is independent of PIK3CG activity. Heterodimer with PALS1. Interacts with DLG5 and NF2. Interacts (via guanylate kinase-like domain) with WHRN (via third PDZ domain). Colocalizes with WHRN at stereocilium tip during hair cell development (PubMed:16829577). Colocalizes with PALS1 in the retina, at the outer limiting membrane (OLM) (PubMed:17584769). Colocalizes with WHRN in the retina, at the outer limiting membrane (OLM), outer plexifirm layer (OPL), basal bodies, and at connecting cilium (CC) (PubMed:17584769). Colocalizes with NF2 in non-myelin-forming Schwann cells (By similarity). Abundantly expressed in the erythrocytes (at protein level). During development of the retina, expression is highest in the inner, neuroblastic layer, while at later stages it is also present in the photoreceptor cell layer. Detected in the eye from 14.5 dpc onwards. Highly expressed in the liver and primitive gut, and at lower levels in the umbilical vein, the ventricular layer of the CNS and upper/lower jaw region. At 14.5 dpc and 16.5 dpc, expression in the liver and stomach is maintained. In addition, expression is present in bone structures (e.g. zygomatic bone, lower jawbone), cranial nerve ganglia [e.g. trigeminal (V) ganglion] and cochlea. The expression in the eye is seen in the neuroblastic layer. At 16.5 dpc and 18.5 dpc, a slightly higher expression is seen in the neuroblastic layer. At 16.5 dpc, strong expression in the upper part of the gut is maintained and with the onset of ossification, expression is seen in all bone structures of the body. At P7 and P90, expression in the eye is seen in the ganglion cell layer, the inner nuclear layer (INL) and photoreceptor cell layer. Palmitoylated. Neutrophils form multiple transient pseudopods upon chemotactic stimulation, and do not migrate efficiently in vitro. Belongs to the MAGUK family.