Expression of Glycoprotein 2 and Its Glycosylation in Human Cowper's Gland.

Glycoprotein 2 (GP2), initially identified as a primary membrane protein of zymogen granules in pancreatic acinar cells, is a marker of intestinal microfold cells (M cells) and involved in bacterial transcytosis in M cells. Recent studies have reported GP2 expression in the pancreas and intestine among various other organs. We aimed to elucidate the expression of GP2 and its glycosylation modifications in human Cowper's glands. We generated an anti-human GP2 monoclonal antibody suitable for formalin-fixed, paraffin-embedded tissue sections. This antibody, designated GP2-71, successfully stained both the plasma membrane and cytoplasm of normal pancreatic acinar cells. Subsequently, we performed GP2-71 immunostaining on normal human Cowper's gland tissues. Our findings revealed that the luminal cell membrane and contents of the Cowper's glands reacted strongly with GP2-71. Moreover, the regions stained with GP2-71 were partially immunostained with the anti-sialyl Lewis x (sLe(x)) monoclonal antibody HECA-452. Furthermore, western blot analysis of protein A-purified GP2-immunoglobulin G fusion proteins demonstrated that GP2 was decorated with HECA-452-positive glycans. Collectively, these findings indicate that GP2 is expressed in human Cowper's glands and is potentially decorated with sLe(x)-related glycans.