Acts as an adapter protein linking the dynein motor complex to various cargos and converts dynein from a non-processive to a highly processive motor in the presence of dynactin. Facilitates and stabilizes the interaction between dynein and dynactin and activates dynein processivity (the ability to move along a microtubule for a long distance without falling off the track) (PubMed:11483508, PubMed:25035494, PubMed:24986880, PubMed:22956769). Facilitates the binding of RAB6A to the Golgi by stabilizing its GTP-bound form (PubMed:25962623). Regulates coat complex coatomer protein I (COPI)-independent Golgi-endoplasmic reticulum transport via its interaction with RAB6A and recruitment of the dynein-dynactin motor complex (PubMed:12447383, PubMed:25962623). Contributes to nuclear and centrosomal positioning prior to mitotic entry through regulation of both dynein and kinesin-1. During G2 phase of the cell cycle, associates with RANBP2 at the nuclear pores and recruits dynein and dynactin to the nuclear envelope to ensure proper positioning of the nucleus relative to centrosomes prior to the onset of mitosis (PubMed:20386726). Interacts with CPNE4 (via VWFA domain) (PubMed:12522145). Interacts with NEK9 (By similarity). Interacts with DCTN2 (PubMed:11483508, PubMed:22956769). Interacts with RAB6A (PubMed:12447383, PubMed:25962623). Interacts with DNAI1 (By similarity). Interacts with DYNLL1, DYNC1H1, DYNC1I2 and DCTN1 (PubMed:22956769). Forms a complex with dynein and dynactin (PubMed:24986880). The dynein-dynactin-BICD2 ternary complex (DDB) binds preferentially to tyrosinated microtubules than to detyrosinated microtubules (PubMed:26968983). Interacts with RANBP2, RAB6A and KIF5A (PubMed:20386726). Interacts with KIF1C (By similarity). In interphase cells mainly localizes to the Golgi complex and colocalizes with dynactin at microtubule plus ends (PubMed:11483508). Localizes to the nuclear envelope and cytoplasmic stacks of nuclear pore complex known as annulate lamellae in a RANBP2-dependent manner during G2 phase of the cell cycle (By similarity). Ubiquitously expressed with high expression in the spinal cord. The fourth coiled coil region is involved in Golgi targeting and in the interaction with DCTN2. Phosphorylated by NEK9 in vitro. Belongs to the BicD family. Extended N-terminus.