Regulatory subunit of the IKK complex. Probably recruits IkappaBalpha/NFKBIA to the complex. May be involved in the organization of the cytomatrix at the nerve terminals active zone (CAZ) which regulates neurotransmitter release. May be involved in vesicle trafficking at the CAZ. May be involved in Rab-6 regulated endosomes to Golgi transport. Part of a complex with CHUK, IKBKB and IKBKG. Interacts with CHUK, IKBKB and IKBKG. The interaction with IKBKG is independent of CHUK and IKBKB. Interacts with NFKBIA. Isoform 4 interacts with PPFIA1, and through its C-terminus with the PDZ domains of RIMS1 and RIMS2. Interacts with ERC2/CAST1. Interacts with the GTB-bound forms of RAB6A isoform 1 and isoform 2 and with RAB6B. The interaction was strongest with RAB6B, followed by RAB6A isoform 2 and weakest with RAB6A isoform 1 (By similarity). Interacts with SDCCAG8. Recruited on Golgi membranes by RAB6A in a GTP-dependent manner (By similarity). Widely expressed. Isoform 2 and isoform 4 are abundantly expressed in brain. Isoform 1 and isoform 3 are predominantly expressed in testis and thyroid, and isoform 1 predominates in other tissues tested. A chromosomal aberration involving ERC1/RAB6IP2 is found in papillary thyroid carcinomas (PTCs). Translocation t(10;12)(q11;p13) involving RET. In vitro, isoform 1, isoform 3 and isoform 5 participating in a ERC1-RET fusion protein activate tyrosine-protein kinase activity. May be produced at very low levels due to a premature stop codon in the mRNA, leading to nonsense-mediated mRNA decay. May be produced at very low levels due to a premature stop codon in the mRNA, leading to nonsense-mediated mRNA decay. May be produced at very low levels due to a premature stop codon in the mRNA, leading to nonsense-mediated mRNA decay. Contaminating sequence. Potential poly-A sequence. Extended N-terminus. Truncated N-terminus.