This entry includes coiled-coil and C2 domain-containing protein 1A/B (CC2D1A/B, also known as Freud-1/2). CC2D1A is involved in many pathways, including nuclear factor kappaB, PDK1/Akt, cAMP/PKA, Notch and bone morphogenetic protein [1]. It is a calcium-regulated repressor of serotonine receptor 5-HT1A and dopamine-D2 receptor expression [2,3]. CC2D1B binds to the 5-HT1A DRE and represses the human 5-HT1A receptor gene to regulate its expression in non-serotonergic cells and neurons [4]. CC2D1A and CC2D1B have also been shown to interact with the CHMP4 family of proteins, the major subunit of the ESCRT-III complex. They may regulate degradation and signaling of EGFR and TLR4 [1]. CC2D1A and CC2D1B share conserved domains, including several DM14 domains that are specific to this protein family, a C-terminal helix-loop-helix domain, and a C2 domain. The CC2D1A C2 domain is thought to be calcium insensitive and it lacks several acidic residues that mediate calcium binding of the PKC C2 domain. The CC2D1B C2 domain appears to be essential for its DNA binding and repressor function; it may mediate protein-protein interactions [5]. Mutations in the CC2D1A gene has been linked to nonsyndromic mental retardation [6,5]. This entry represents the helical DM14 domain, unique to this family of proteins which is present four times. The function is not known but they seem to be important for NF-kB activation [7].

1: CC2D1A and CC2D1B regulate degradation and signaling of EGFR and TLR4. Deshar R, Cho EB, Yoon SK, Yoon JB; Biochem Biophys Res Commun. 2016;480:280-287. PMID:27769858

2: Freud-1: A neuronal calcium-regulated repressor of the 5-HT1A receptor gene. Ou XM, Lemonde S, Jafar-Nejad H, Bown CD, Goto A, Rogaeva A, Albert PR; J Neurosci. 2003;23:7415-7425. PMID:12917378

3: Differential repression by freud-1/CC2D1A at a polymorphic site in the dopamine-D2 receptor gene. Rogaeva A, Ou XM, Jafar-Nejad H, Lemonde S, Albert PR; J Biol Chem. 2007;282:20897-20905. PMID:17535813

4: Human Freud-2/CC2D1B: a novel repressor of postsynaptic serotonin-1A receptor expression. Hadjighassem MR, Austin MC, Szewczyk B, Daigle M, Stockmeier CA, Albert PR; Biol Psychiatry. 2009;66:214-222. PMID:19423080

5: The Freud-1/CC2D1A family: transcriptional regulators implicated in mental retardation. Rogaeva A, Galaraga K, Albert PR; J Neurosci Res. 2007;85:2833-2838. PMID:17394259

6: The CC2D1A, a member of a new gene family with C2 domains, is involved in autosomal recessive non-syndromic mental retardation. Basel-Vanagaite L, Attia R, Yahav M, Ferland RJ, Anteki L, Walsh CA, Olender T, Straussberg R, Magal N, Taub E, Drasinover V, Alkelai A, Bercovich D, Rechavi G, Simon AJ, Shohat M; J Med Genet. 2006;43:203-210. PMID:16033914

7: CC2D1A, a DM14 and C2 domain protein, activates NF-kappaB through the canonical pathway. Zhao M, Li XD, Chen Z; J Biol Chem. 2010;285:24372-24380. PMID:20529849