Mucin 1 cytoplasmic domain (MUC1-C (cytoplasmic domain))

The **Mucin 1 cytoplasmic domain** (MUC1-C cytoplasmic domain) is the short, 72-amino-acid intracellular tail of the membrane-tethered subunit of the transmembrane glycoprotein Mucin 1 (MUC1), a member of the mucin family widely expressed on epithelial tissues and aberrantly overexpressed in many carcinomas[1][2][4][6]. MUC1 is synthesized as a single polypeptide, then undergoes autoproteolytic cleavage to form the large extracellular MUC1-N subunit and the membrane-bound C-terminal MUC1-C subunit, which contains a short extracellular stem, a 28-amino-acid transmembrane region, and the 72-residue cytoplasmic domain[3][6][7]. The MUC1-C cytoplasmic domain is intrinsically disordered, except for the highly conserved CQCRRK motif near the membrane, which forms a possible druggable pocket for inhibitors[1][6]. The MUC1-C cytoplasmic region is phosphorylated by several kinases and functions as a scaffold for the assembly of key signaling complexes relevant to tumor cell survival, proliferation, apoptosis resistance, and epithelial-mesenchymal transition[3][6][7][8]. It can interact with and regulate proteins such as EGFR, Src, PKCδ, GSK3β, β-catenin, p53, and NF-κB, influencing multiple oncogenic and inflammatory signaling pathways and gene expression[2][4][5][8]. Overexpression and/or aberrant glycosylation of MUC1-C is associated with tumor progression, metastasis, immune evasion (e.g., through PD-L1 induction), and drug resistance, making it a validated therapeutic target, particularly in breast, lung, and other carcinomas as well as some hematologic malignancies[2][5][6]. Efforts to therapeutically target MUC1-C include small molecules, peptides (which disrupt the CQC motif and prevent dimerization), and monoclonal antibodies (such as 3D1) that block cell surface or intracellular functions[1][7]. Note: There are currently no FDA-approved drugs directly targeting the MUC1-C cytoplasmic domain, but several candidates (peptides, antibodies, vaccine-based approaches) are in preclinical or early clinical development[1][6][7].

Other names

MUC1-CMUC1 cytoplasmic tailMUC1 C-terminalMucin 1 C-terminal subunit (cytoplasmic domain)

Inhibition of MUC1-C dimerization (peptides), blockade of MUC1-C signaling and nuclear translocation (peptides, antibodies), antibody-dependent cell-mediated cytotoxicity (antibodies)