The folding and cell surface expression of CD4 requires glycosylation

• Published in: The Journal of biological chemistry Vol. 267; no. 5; pp. 3268 - 3273
• Main Authors: Tifft, C J, Proia, R L, Camerini-Otero, R D
• Format: Journal Article
• Language: English
• Published: Bethesda, MD American Society for Biochemistry and Molecular Biology 15.02.1992
• Subjects: Amino Acid Sequence; Analytical, structural and metabolic biochemistry; Antigens, CD - biosynthesis; Base Sequence; Biological and medical sciences; CD4 antigen; CD4 Antigens - genetics; CD4 Antigens - metabolism; Cell Membrane - immunology; expression; Flow Cytometry; Fluorescent Antibody Technique; folding; Fundamental and applied biological sciences. Psychology; Glycoproteins; Glycosylation; HeLa Cells; Humans; Molecular Sequence Data; Mutagenesis, Site-Directed; Oligodeoxyribonucleotides; Protein Biosynthesis; Protein Conformation; Protein Processing, Post-Translational; Proteins; T-Lymphocytes - physiology; Transcription, Genetic; Transfection; Human; Intracellular transport; Refolding; T-Lymphocyte; Site directed mutagenesis; Glycoproteins; Glycosylation; Molecular targeting; Cell surface
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(19)50726-8

Human CD4, a monomeric T cell surface glycoprotein, is required for T helper cell activation and is also the receptor for the human immunodeficiency virus. There have been conflicting reports as to whether glycosylation of CD4 is required for its cell surface expression. To clarify the effect of glycosylation on surface expression, folding, and intracellular sorting of CD4, we generated a series of mutant cDNAs in which one, the other, or both glycosylation recognition sites were eliminated. Using in vitro transcription and translation we confirmed that both potential glycosylation sites of CD4 were utilized. Transient expression of the mutants in HeLa cells demonstrated that glycosylation at either site was necessary and sufficient for cell surface expression. Finally, we showed that unglycosylated CD4 produced in HeLa cells was incorrectly folded and retained intracellularly, probably in the endoplasmic reticulum.