Together with BCAR1 it may play a role in the control of epithelial cell polarity (By similarity). Involved in the organization of apical junctions in kidney cells together with NPHP4 and RPGRIP1L/NPHP8 (By similarity). Does not seem to be strictly required for ciliogenesis (By similarity). Seems to help to recruit PTK2B/PYK2 to cell matrix adhesions, thereby initiating phosphorylation of PTK2B/PYK2 and PTK2B/PYK2-dependent signaling (By similarity). May play a role in the regulation of intraflagellar transport (IFT) during cilia assembly (By similarity). Required for normal retina development (By similarity). In connecting photoreceptor cilia influences the movement of some IFT proteins such as IFT88 and WDR19. Involved in spermatogenesis (By similarity). Interacts with Crk-associated substrate BCAR1, NPHP4, PTK2B/PYK2 and tensin. Interacts with INVS and NPHP3. Interacts with AHI1 and TNK2 (By similarity). Interacts with NPHP4 in a complex containing NPHP1, NPHP4 and RPGRIP1L/NPHP8 (By similarity). Interacts with IQCB1; the interaction likely requires additional interactors (By similarity). Interacts with KIF7 (By similarity). Interacts with ANKS3 (By similarity). Interacts with SPATA7 (By similarity). Interacts with FLNA (By similarity). In the retinal photoreceptor cell layer, localizes at the connecting cilium (By similarity). Colocalizes with E-cadherin and BCAR1 at or near the cell-cell adherens junctions (By similarity). Localizes to respiratory cilia axoneme (By similarity). Localized to the transition zone of respiratory cilia (By similarity). Localized to the transition zone of photoreceptor-connecting cilia and renal monocilia (By similarity). In cultured renal cells, it localizes diffusely in the cytoplasm but, as cells approach confluence, it accumulates to basolateral tight junctions (By similarity). Expressed in renal cells (at protein level). The SH3 domain mediates the stable interaction with Cas. Belongs to the nephrocystin-1 family.