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Journal of Virology, October 1999, p. 8677-8688, Vol. 73, No. 10
Department of Stomatology, School of
Dentistry, University of California San Francisco, San Francisco,
California 94143-0512
Received 2 March 1999/Accepted 17 June 1999
We previously reported that human cytomegalovirus (CMV)
glycoprotein B (gB) is transported to apical membranes in CMV-infected polarized retinal pigment epithelial (ARPE-19) cells and in Madin-Darby canine kidney (MDCK) epithelial cells constitutively expressing gB. The
cytosolic domain of gB contains a cluster of acidic amino acids, a
motif that plays a pivotal role in vectorial trafficking in polarized
epithelial cells and may also function as a signal for entry into the
endocytic pathway. Here we compared gB internalization and recycling to
the plasma membrane in CMV-infected human fibroblasts (HF) and ARPE-19
cells by using antibody-internalization experiments. Immunofluorescence
and quantitative assays showed that gB was internalized from the cell
surface into clathrin-coated transport vesicles and then recycled to
the plasma membrane. gB colocalized with clathrin-coated vesicles
containing the transferrin receptor in the early endocytic/recycling
pathway, indicating that gB traffics in this pathway. The specific role
of the acidic cluster in regulating the sorting of gB-containing
vesicles in the early endocytic/recycling pathway was examined in MDCK
cells expressing mutated gB derivatives. Immunofluorescence assays
showed that derivatives lacking the acidic cluster were impaired in
internalization and failed to recycle. These findings, together with
our earlier observation that the acidic cluster is a key determinant
for targeting gB molecules to apical membranes in epithelial cells,
establish that this signal is recognized by cellular proteins that
participate in polarized sorting and transport in the early
endocytic/recycling pathway.
0022-538X/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
An Acidic Cluster in the Cytosolic Domain of Human
Cytomegalovirus Glycoprotein B Is a Signal for Endocytosis from the
Plasma Membrane
*
Corresponding author. Mailing address: Department of
Stomatology, School of Dentistry, University of California San
Francisco, 513 Parnassus Ave., San Francisco, CA 94143-0512. Phone:
(415) 476-8248. Fax: (415) 502-7338. E-mail:
pereira{at}itsa.ucsf.edu.
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