Acts in a planar cell polarity (PCP) complex; polarization along the apical/basal axis of epithelial cells. Correct expression of the alternative isoforms is required for PCP signaling in imaginal disks. PCP signaling in the wing disk requires the receptor fz and the cytoplasmic proteins dsh and pk. These act in a feedback loop leading to activation of the jnk cascade and subsequent polarized arrangement of hairs and bristles. Dgo and pk compete with one another for dsh binding, thereby modulating fz dsh activity and ensuring tight control over fz PCP signaling. Vang, stan and pk function together to regulate the establishment of tissue polarity in the adult eye. Interacts with dsh; PET and LIM domains interact with dsh DEP domain, in wing cells. Interacts with Vang in photoreceptor cells. Localized to the proximal wing cell boundary where fz and dsh localization is antagonized by binding the dsh DEP domain and preventing dsh cortical localization. Localization to the anterior photoreceptor cell membrane. Expressed in the wing, leg and eye imaginal disks. Expressed within the photoreceptors of the eye. Expressed both maternally and zygotically. Isoform B is expressed in embryos only. Isoform A and isoform C are expressed in embryos and pupae. Flies exhibit aberrant hair and bristle orientation on the wings and aberrant ommatidial arrangement in the compound eye. Belongs to the prickle / espinas / testin family.