GP2

GP2 Full Name

glycoprotein 2 (zymogen granule membrane)

GP2 Introduction

GP2 (Glycoprotein 2) is located on chromosome 16p12.3 and spans approximately 17.9 kb, containing 11 exons that encode multiple transcript variants through alternative splicing. The gene produces a 530-amino acid precursor protein that undergoes extensive post-translational modification, including N-linked glycosylation at eight sites and proteolytic cleavage of an N-terminal signal peptide. The mature protein features several conserved structural domains: an N-terminal D8C domain containing eight conserved cysteines predicted to form four disulfide bridges, followed by an EGF-like domain and a C-terminal zona pellucida (ZP) domain essential for polymerization. The C-terminus contains a glycosylphosphatidylinositol (GPI) anchor signal sequence that directs membrane attachment, with a 20-residue hydrophobic transmembrane domain preceded by a decapeptide containing potential GPI-anchor attachment sites.

Figure 1.Domain structures of GP2 (upper left) and uromodulin (lower left).(Lin Y, 2021)

Tissue-Specific Expression and Subcellular Localization
GP2 exhibits highly restricted tissue expression, with the pancreas showing the highest levels at approximately 9286 RPKM, representing the most abundant membrane protein in pancreatic zymogen granules. Within pancreatic acinar cells, GP2 localizes to the membrane of zymogen granules, where it serves as the major integral membrane glycoprotein. The protein exists in two forms: a membrane-bound GPI-anchored form on granule membranes and a soluble form released into pancreatic juice following enzymatic cleavage by endogenous phospholipases or carboxypeptidases. Beyond the pancreas, GP2 is also expressed on the apical surface of M cells in Peyer's patches of the small intestine, where it functions as a transcytotic receptor, and has been detected on activated T lymphocytes.

Clinical Significance as a Diagnostic and Prognostic Marker
GP2 has emerged as a clinically valuable biomarker across multiple gastrointestinal and autoimmune disorders. In acute pancreatitis, the alpha isoform of GP2 (GP2a) is released from damaged acinar cells into the bloodstream, where elevated serum concentrations serve as a specific diagnostic marker with excellent sensitivity and specificity shortly after disease onset, and correlate with disease severity and prognosis. GP2 also functions as a major autoantigen in inflammatory bowel disease, with anti-GP2 antibodies detected in Crohn's disease patients where they are associated with more severe disease course and may neutralize the protective functions of pancreatic and M cell GP2. The protein is a component of intraductal protein plugs in chronic pancreatitis, where it accumulates similarly to its homolog uromodulin in renal casts, suggesting a role in ductal obstruction pathogenesis. Additionally, GP2 autoantibodies have been identified in primary sclerosing cholangitis and are associated with progressive disease, while GP2 expression on colorectal cancer cells promotes proliferation and metastasis through Notch pathway modulation.

Alternate Names for GP2

GP2; glycoprotein 2 (zymogen granule membrane); ZAP75; pancreatic secretory granule membrane major glycoprotein GP2; pancreatic zymogen granule membrane protein GP-2; pancreatic zymogen granule membrane associated protein GP2;