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Journal of Virology, May 1999, p. 3789-3799, Vol. 73, No. 5
Laboratoire Rétrovirus et Transfert
Génétique, CNRS URA 1157, Institut Pasteur, 75724 Paris, France
Received 4 September 1998/Accepted 19 January 1999
PIT-2 is a type III sodium phosphate cotransporter and the receptor
for amphotropic murine leukemia viruses. We have investigated the
expression and the functions of a tagged version of PIT-2 in CHO cells.
PIT-2 remained equally abundant at the cell surface within 6 h
following variation of the phosphate supply. In contrast, the efficiency of phosphate uptake and retrovirus entry was inversely related to the extracellular phosphate concentration, indicating that PIT-2 activities are modulated by posttranslational modifications of cell surface molecules induced by phosphate. Conformational changes
of PIT-2 contribute to both activities, as shown by the inhibitory
effect of sulfhydryl reagents known as inhibitors of type II
cotransporters. A physical association of PIT-2 with actin was
demonstrated. Modifications of the actin network were induced by
variations of the concentrations of extracellular phosphate, cytochalasin D, or lysophosphatidic acid. They revealed that the formation of actin stress fibers determines the cell surface
distribution of PIT-2, the internalization of the receptor in response
to virus binding, and the capacity to process retrovirus entry. Thus,
the presence of PIT-2 at the cell surface is not sufficient to ensure phosphate transport and susceptibility to amphotropic retrovirus infection. Further activation of cell surface PIT-2 molecules is
required for these functions.
0022-538X/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Modulation of Phosphate Uptake and Amphotropic
Murine Leukemia Virus Entry by Posttranslational Modifications
of PIT-2
*
Corresponding author. Mailing address: Laboratoire
Rétrovirus et Transfert Génétique, Institut Pasteur,
28 Rue du Dr. Roux, 75724 Paris, France. Phone: 33 (0) 1 45 68 82 46. Fax: 33 (0) 1 45 68 89 40. E-mail: jmheard{at}pasteur.fr.
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