Proposed scaffold protein that is implicated in diverse physiological processes and whose function may be in part linked to its ability to regulate ubiquitination of specific cellular proteins. Can modulate activity of cullin-RING E3 ubiquitin ligase (CRL) complexes by displacing CAND1; in vitro promotes CRL E3 activity and dissociates CAND1 from CUL1 and CUL2. Promotes ubiquitination of NF-kappa-B subunit RELA and its subsequent proteasomal degradation. Down-regulates NF-kappa-B activity. Involved in the regulation of membrane expression and ubiquitination of SLC12A2. Modulates Na(+) transport in epithelial cells by regulation of apical cell surface expression of amiloride-sensitive sodium channel (ENaC) subunits and by promoting their ubiquitination presumably involving NEDD4L. Promotes the localization of SCNN1D to recycling endosomes. Promotes CFTR cell surface expression through regulation of its ubiquitination. Down-regulates SOD1 activity by interfering with its homodimerization. Plays a role in copper ion homeostasis. Involved in copper-dependent ATP7A trafficking between the trans-Golgi network and vesicles in the cell periphery; the function is proposed to depend on its association within the CCC complex and cooperation with the WASH complex on early endosomes. Can bind one copper ion per monomer. May function to facilitate biliary copper excretion within hepatocytes. Binds to phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2). Involved in the regulation of HIF1A-mediated transcription; competes with ARNT/Hif-1-beta for binding to HIF1A resulting in decreased DNA binding and impaired transcriptional activation by HIF-1. Negatively regulates neuroblastoma G1/S phase cell cycle progression and cell proliferation by stimulating ubiquitination of NF-kappa-B subunit RELA and NF-kappa-B degradation in a FAM107A- and actin-dependent manner. Monomer, homodimer. Can form heterodimers with other COMM domain-containing proteins but only certain combinations may exist in vivo. Interacts (via COMM domain) with COMMD2, COMMD3, COMMD4, COMMD5, COMMD6, COMMD7, COMMD8 and COMMD10 (via COMM domain). Identified in a complex with an E3 ubiquitin ligase complex composed of TCEB1/elongin C, CUL2, SOCS1 and RBX1; in the complex interacts directly with SOCS1 and CUL2. Interacts directly with ATP7B (via the N-terminal region). Interacts with CCS, CDKN2A, RELA, REL, RELB, NFKB1/p105, NFKB2/p100, NFKBIB, SCNN1D, SCNN1B, CFTR, CLU, SGK1, AKT1, CUL1, CUL2, CUL3, CUL4A, CUL4B, CUL5, CUL7, HIF1A. Identified in a complex with NF-kappa-B. Interacts directly with SLC12A2. Interacts with CCDC22 and CCDC93; proposed to be a component of the CCC (COMMD/CCDC22/CCDC93) complex which contains at least COMMD1 (and possibly other COMM domain-containing proteins), CCDC22, CCDC93. Interacts with VPS35L; the interaction associates CCC complex with retriever complex. Interacts with ATP7A. Interacts with FAM107A; this interaction stabilizes COMMD1 in the nucleus. Shuttles between nucleus and cytosol. Detected in perinuclear foci that may be aggresomes containing misfolded, ubiquitinated proteins (By similarity). Ubiquitinated; undergoes both 'Lys-63'- and 'Lys-48'-linked polyubiquitination. Ubiquitinated by XIAP, leading to its proteasomal degradation (By similarity).