UNIPROT #

P98088

PROTEIN NAME

MUC5AC

SYNONYMS

Apomucin antibody; Apomucin Major Airway Glycoprotein antibody; Gastric mucin antibody; LeB antibody; Lewis B blood group antigen antibody; Major Airway Glycoprotein antibody; MUC 5 antibody; MUC5 antibody; MUC5AC antibody; Mucin 5 subtype AC tracheobronchial antibody; Mucin 5 Subtypes A And C antibody; Mucin 5 subtypes A and C tracheobronchial/gastric antibody; Mucin 5, tracheobronchial/gastric antibody; Mucin 5AC antibody; Mucin 5AC oligomeric mucus/gel forming antibody; Mucin 5AC, oligomeric mucus/gel forming pseudogene antibody; Mucin antibody; TBM antibody; Tracheobronchial Mucin (TBM) antibody; Tracheobronchial mucin antibody

TISSUE SPECIFICITY

Highly expressed in surface mucosal cells of respiratory tract and stomach epithelia. Overexpressed in a number of carcinomas. Also expressed in Barrett's esophagus epithelium and in the proximal duodenum.

POST-TRANSLATIONAL MODIFICATION

C-, O- and N-glycosylated. O-glycosylated on the second and last Thr of the Thr-/Ser-rich tandem repeats TTPSPVPTTSTTSA. One form of glycosylation is also known as Lewis B (LeB) blood group antigen, a tetrasaccharide consisting of N-acetylglucosamine having a fucosyl residue attached. It has a role as an epitope and antigen and functions as a receptor for H.pylori binding and facilitates infection. C-mannosylation in the Cys-rich subdomains may be required for proper folding of these regions and for export from the endoplasmic reticulum during biosynthesis.; Proteolytic cleavage in the C-terminal is initiated early in the secretory pathway and does not involve a serine protease. The extent of cleavage is increased in the acidic parts of the secretory pathway. Cleavage generates a reactive group which could link the protein to a primary amide.

SUBCELLULAR LOCATION

Secreted.

FUNCTION

Mucins are a group of high molecular weight glycoproteins consisting of a mucin core protein and O-linked carbohydrates. Mucin 6 carries GlcNAca1-->4Galb-->R structures, indicating that alpha1, 4-N-acetylglucosaminyltransferase is important to the formation of the mucous glycoproteins in vivo. Mucin 5AC is a gel-forming mucin that is secreted from surface mucous cells. Glucocorticoid is required for the expression of Mucin 5AC mRNA and high doses of hydrocortisone suppress its expression. Additionally, asthmatic fluid stimulates Mucin 5AC synthesis several-fold. The pro-inflammatory cytokines IL-6 and TNF-alpha stimulate Mucin 5AC secretion and thus contribute to the upregulation of mucin by chronic inflammation. Expression of Mucin 5AC is retinoic acid (RA)- or retinol- dependent and RA control of mucin genes is mediated by the retinoid acid receptor RARα and, to a lesser extent, by RARγ. Thyroid hormone binding to thyroid receptors inhibits Mucin 5AC gene expression. Mucin 5AC is also expressed in normal endocervical epithelium, small intestine, gastric cells (Lewis type 1) and gastric metaplasia, and it is a one of the major mucins in the ethmoid mucosa.