Post-translational protein modification and expression of ankyrin-binding site(s) in GP85 (Pgp-1/CD44) and its biosynthetic precursors during T-lymphoma membrane biosynthesis.

Abstract

In this study, we have investigated the biosynthesis and processing of GP85 (Pgp-1/CD44), a lymphoma transmembrane glycoprotein known to contain ankyrin-binding site(s). Using a standard pulse-chase protocol, we have detected a 52-kDa polypeptide precursor (p52) within the first 5 min of pulse labeling which contains a high mannose-type N-linked oligosaccharide chains. The conversion of p52 to GP85 requires further glycosylation (both complex type N-linked and O-linked) which takes place in the Golgi complex within 10-20 min after p52 is synthesized. GP85 is then incorporated into the plasma membrane where its turnover rate is relatively slow, a t1/2 of approximately 8 h. Following tunicamycin treatment, we have detected two other precursor proteins: p42 which is unglycosylated and p58 which is O-glycosylated. p42 appears to be an immediate precursor of p52 because p52 is converted to p42 upon deglycosylation. Therefore, the biosynthesis of GP85 appears to occur in the following sequence: p42 in equilibrium to p52 in equilibrium to GP85. Further analysis reveals that all of the GP85 precursors (i.e. p42, p52, and p58) contain ankyrin-binding site(s). Chemical composition analysis of GP85 indicates that this molecule contains approximately 3 N-linked and 4-5 O-linked oligosaccharide chains. Although neither N-glycosylation nor O-glycosylation appears to play an important role in the formation of ankyrin-binding site(s), O-glycosylation (and to a lesser extent N-glycosylation) of GP85 is required for T-lymphoma cell surface interaction with both collagen and hyaluronic acid. These findings suggest that GP85 (Pgp-1/CD44) and its biosynthetic precursors play a pivotal role in regulating adhesion functions such as lymphocyte homing and binding to the extracellular matrix.

• Authors: V B Lokeshwar, L Y Bourguignon
• Journal: The Journal of biological chemistry (J Biol Chem) Vol. 266 Issue 27 Pg. 17983-9 (Sep 25 1991) ISSN: 0021-9258 [Print] United States
• PMID: 1833390 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• Ankyrins
• Blood Proteins
• Membrane Glycoproteins
• Membrane Proteins
• Protein Precursors
• Receptors, Lymphocyte Homing
• Tunicamycin
• Monensin

Topics

• Animals
• Ankyrins
• Binding Sites
• Blood Proteins (metabolism)
• Cell Membrane (metabolism)
• Glycosylation
• Lymphoma, T-Cell (metabolism)
• Membrane Glycoproteins (biosynthesis, metabolism)
• Membrane Proteins (metabolism)
• Mice
• Monensin (pharmacology)
• Precipitin Tests
• Protein Precursors (metabolism)
• Protein Processing, Post-Translational
• Receptors, Lymphocyte Homing (biosynthesis, metabolism)
• Tunicamycin (pharmacology)