Required for the morphological differentiation and maintenance of the rhabdomeric photoreceptor apical domain (PubMed:32579558). Acts as a downstream component of the gl and Pph13 transcriptional pathway which is required for photoreceptor cell development (PubMed:32579558). Likely to function by regulating the trafficking or retention of rhabdomeric proteins including the phototransduction proteins ninaE and didum (PubMed:32579558). Cortical membrane protein (PubMed:26481050, PubMed:32579558). In photoreceptors, restricted to the rhabdomeric portion of the apical surface (PubMed:32579558). Phosphorylation appears to displace it from the cortex, increasing cytosol levels (PubMed:26481050, PubMed:32579558). Restricted to photoreceptor cells (at protein level) (PubMed:32579558). Not detected until approximately 48hrs after puparium formation (APF) and then maintained in the photoreceptor cells post-eclosion (at protein level) (PubMed:32579558). The phospho-regulated basic and hydrophobic (PRBH) motif is sufficient and important for interaction with phospholipids permitting cortical localization (PubMed:26481050). Phosphorylation of the PRBH motif by aPKC inhibits the association of the protein with the cortical membrane (PubMed:26481050, PubMed:32579558). Phosphorylated by aPKC which lowers lipid affinity and promotes dissociation from the cell cortex (PubMed:26481050, PubMed:32579558). In the photoreceptor cells, aPKC-mediated phosphorylation leads to its displacement from the stalk apical cortex and thus restricts its localization to the rhabdomeric apical cortex where it functions (PubMed:32579558). Dephosphorylation appears to be light-dependent (PubMed:9697866). Viable however, rhabdomeres are flat and oblong, and alignment or organization of the microvillar projections along the depth of the retina are not maintained (PubMed:32579558). Severity of the phenotype increases with age, by seven days post-eclosion rhabdomeres have become irregular, misaligned and fragmented structures (PubMed:32579558). The phototransduction proteins ninaE and, to a much lesser extent, didum are displaced from vesicles near the rhabdomere terminal web and instead become mislocalized to the basal lateral membranes (PubMed:32579558). Photoactivation of ninaE and phototransduction are unaffected, and amplitudes of light response is enhanced at higher light intensities (PubMed:32579558).