AEGiS-06IAC: Lateral diffusion of CD4 on the surface of human neoplastic T-cell line probed with a fluorescent derivative of the envelope glycoprotein (gp120) of human immunodeficiency virus type 1 (HIV-1).

6th International AIDS Conference

San Francisco, California, USA — June 20-23, 1990

Lateral diffusion of CD4 on the surface of human neoplastic T-cell line probed with a fluorescent derivative of the envelope glycoprotein (gp120) of human immunodeficiency virus type 1 (HIV-1).

Int Conf AIDS 1990 Jun 20-23; 6:314 (abstract no. 1001)
Pal R, Nair BC, Hoke G, Sarngadharan M, Edidin M; Advanced BioScience Laboratories, Inc., Kensington, MD, USA

OBJECTIVE: To study the lateral diffusion of CD4 molecule on the surface of human T-cell line by using fluorescein-labeled gp120 of HIV-1.

METHODS: Envelope glycoprotein (gp120) was labeled with fluorescein using 6-(4,6 dichlorotriazinyl) amino fluorescein. The syncytium assay was performed by co-cultivation of HIV-1-infected cells with CEM cells. Later diffusion of CD4 was measured by fluorescence photobleaching recovery (FPR) method.

RESULTS: Fluorescein-labeled gp120 was found to bind to CD4+ CEM cells and inhibited syncytium formation normally observed when HIV-1-infected cells are co-cultured with CEM cells. Fluorescence photobleaching recovery measurements showed that the diffusion coefficient (D) of CD4 complexed with fluorescein-labeled gp120 was around 5x10(-10) cm(2) sec(-1), with nearly 61% of the receptor molecules being mobile. Binding of anti-gp120 monoclonal antibody to the CD4-gp120 complex reduced the mobile fraction to a significant extent. Diffusion of CD4 labeled with OKT4 IgG was markedly inhibited with reductions in both D and mobile fraction but such inhibition was not observed with OKT4 Fab.

CONCLUSION: Crosslinking of multiple molecules of CD4 by OKT4 antibody is required to reduce CD4 mobility. The receptor might be present on the membrane plane as molecular clusters containing at least two molecules of CD4. Such dimers of CD4 when complexed with two molecules of gp120 would be readily aggregated when crosslinked with anti-glycoprotein antibodies resulting in the immobilization of the receptor.

900620
1001