Component of the nexin-dynein regulatory complex (N-DRC), a key regulator of ciliary/flagellar motility which maintains the alignment and integrity of the distal axoneme and regulates microtubule sliding in motile axonemes. Plays an important role in the assembly of the N-DRC linker (By similarity). Plays dual roles at both the primary (or non-motile) cilia to regulate hedgehog signaling and in motile cilia to coordinate cilia movement. Required for proper motile cilia functioning (PubMed:26387594, PubMed:27120127, PubMed:27472056). Positively regulates ciliary smoothened (SMO)-dependent Hedgehog (Hh) signaling pathway by facilitating the trafficking of SMO into the cilium and the stimulation of SMO activity in a GRK2-dependent manner (By similarity). Component of the nexin-dynein regulatory complex (N-DRC). Interacts with microtubules (By similarity). Interacts with SMO (PubMed:21659505). Interacts (via coiled-coil domains) with RAB3B (in GTP-bound form) (By similarity). Interacts with DRC7 (By similarity). Associates with microtubules (PubMed:10969087). Localized to the cytoplasm of round spermatids, the tails of elongating spermatids, and mature spermatid tail bundles protruding into the lumen, and in the flagellum of epididymal spermatozoa (By similarity). Expressed in respiratory epithelial cells (at protein level) (PubMed:26387594). Expressed in the heart, skeletal muscle, pancreas, liver, brain, trachea and lung. Weakly or not expressed in placenta and kidney (PubMed:9790751). The disease is caused by variants affecting the gene represented in this entry. Belongs to the DRC4 family.