MUC3

MUC3 encodes a membrane-associated intestinal mucin that contributes to the protective glycocalyx and epithelial surface barrier of the gastrointestinal tract, where extensive glycosylation and transmembrane localization support mucosal homeostasis and host-environment interactions^[1][2]. Mechanistically, MUC3 proteins belong to the membrane-bound mucin family and contain characteristic extracellular mucin domains together with SEA and transmembrane regions, linking epithelial protection with cell-surface signaling functions^[3][4]. In intestinal epithelial cells, MUC3A is predominantly expressed in the small intestine and colon, and its transcription is regulated by conserved intestinal transcriptional programs involving factors such as HNF4A, HNF4G, and STAT3^[5]. Disease-associated studies further indicate that elevated MUC3A expression can promote tumor progression through pathways including PI3K/Akt/mTOR and NF-κB, supporting its relevance in colorectal and non-small-cell lung cancer models^[6][7]. Compared with related isoforms, the distinction between MUC3A and MUC3B is a major research focus. Genomic and transcriptomic analyses demonstrated that MUC3A and MUC3B are distinct but highly homologous membrane mucin genes, sharing conserved regulatory elements while maintaining separate transcriptional products in human intestinal tissues^[4][5][8]. MUC3B exhibits strong structural similarity to MUC3A but contains an expanded tandem-repeat region, providing a useful model for studying mucin evolution, glycosylation diversity, and epithelial barrier biology^[5]. For experimental applications, MUC3A and MUC3B expression, genetic variation, and pathway activity are commonly investigated as biomarkers or mechanistic readouts in intestinal biology and cancer research^[5][6][7].