Increased N-acetyl-β-glucosaminidase activity in primary breast carcinomas corresponds to a decrease in N-acetylglucosamine containing proteins

Abstract

N-acetylglucosamine (O-GlcNAc) modification on serine or threonine residues of cytoplasmic and nuclear proteins has become a more recognized intracellular covalent modification. Removal of this modification is carried out by N-acetyl-beta-glucosaminidase (O-GlcNAcase). Since little information exists on monoglycosylation and O-GlcNAcase activity in mitogenic systems, we investigated O-GlcNAcase activity in primary breast tumors compared to matched normal adjacent breast tissue and examined enzymatic activity in relationship to the level of protein monoglycosylation. Using a variation of the acidic hexosaminidase activity assay, we demonstrated an increase in both O-GlcNAcase and lysosomal hexosaminidase activity in breast tumor tissue compared to matched adjacent tissue. Although no clear correlation with tumor grade or type was apparent among the samples examined (12 matched pairs), the increase in O-GlcNAcase and lysosomal hexosaminidase activity in tumor tissue was consistently elevated and statistically significant (P<0.05). Protein monoglycosylation was evaluated using immunoblotting, affinity blotting, and radioactive labeling. While the variety of modified proteins was greater in tumor tissue compared to adjacent tissue, the total amount of O-GlcNAc monoglycosylation was significantly decreased in the tumor tissue especially on proteins in the molecular mass range of 45-65 kDa. O-GlcNAcase may be involved in the selective removal of O-GlcNAc on certain proteins in breast tumor tissue.

O-GlcNAcylation Determines the Solubility, Filament Organization, and Stability of Keratins 8 and 18*

“…Malignant transformation appears to be associated with increased activity of O-GlcNAcase, thereby leading to decreased O-GlcNAc on cellular proteins (46). By comparing the hepatoma (HepG2) cell line with the immortalized hepatocytes (Chang), we demonstrate that this decrease is evident even in the transformed hepatoma cell line (supplemental Fig.…”

“…Cancer cells also show decreased O-GlcNAcylation on several cellular proteins because of increased activity of O-GlcNAcase (46). It would thus be important to investigate whether reduced O-GlcNAc on K8 and K18 is the cause of their accumulation as aggregates in cancer cells.…”

“…Their Solubility-Malignant transformation reportedly results in increased activity of the enzyme O-GlcNAcase leading to decreased O-GlcNAcylation on cellular proteins (46). This decrease in O-GlcNAcylation on cellular proteins is seen even in highly malignant HepG2 (hepatoma) cell line as compared with the immortalized Chang cells (hepatocyte) (supplemental Fig.…”

O-GlcNAcylation enhances anaplastic thyroid carcinoma malignancy

“…The enhancement of its degradative activity has been observed to be associated with O-GlcNAcylation level in a variety of human cancer types (21)(22)(23)(24)(25)(26)(27)(28)(29)(30). Additionally, a previous study proposed OGA activity to be significantly higher and O-GlcNAcylation to be lower in tumor tissue compared with corresponding normal tissue (31). Similarly, a different study demonstrated increased activity of OGA A B activity and decreased O-GlcNAc levels in thyroid cancer compared with benign lesions (16).…”

Elevation of nucleocytoplasmic β-N-acetylglucosaminidase (O-GlcNAcase) activity in thyroid cancers

“…O-GlcNAcase activity was measured in supernatant samples of thyroid lesions in two different ways. In the first case, the assay was based on the method described by Slawson et al (25). Two supernatant samples sets were prepared.…”