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Journal of Virology, April 2001, p. 3896-3902, Vol. 75, No. 8
James A. Baker Institute, College of
Veterinary Medicine, Cornell University, Ithaca, New York
14853,1 and Laboratory of Genomic
Diversity, National Cancer Institute, Frederick, Maryland
217022
Received 8 November 2000/Accepted 22 January 2001
Canine parvovirus (CPV) enters and infects cells by a
dynamin-dependent, clathrin-mediated endocytic pathway, and viral
capsids colocalize with transferrin in perinuclear vesicles of cells
shortly after entry (J. S. L. Parker and C. R. Parrish,
J. Virol. 74:1919-1930, 2000). Here we report that CPV and feline
panleukopenia virus (FPV), a closely related parvovirus, bind to the
human and feline transferrin receptors (TfRs) and use these receptors
to enter and infect cells. Capsids did not detectably bind or enter
quail QT35 cells or a Chinese hamster ovary (CHO) cell-derived cell line that lacks any TfR (TRVb cells). However, capsids bound and were
endocytosed into QT35 cells and CHO-derived TRVb-1 cells that expressed
the human TfR. TRVb-1 cells or TRVb cells transiently expressing the
feline TfR were susceptible to infection by CPV and FPV, but the
parental TRVb cells were not. We screened a panel of feline-mouse
hybrid cells for susceptibility to FPV infection and found that only
those cells that possessed feline chromosome C2 were susceptible. The
feline TfR gene (TRFC) also mapped to feline chromosome C2. These data
indicate that cell susceptibility for these viruses is determined by
the TfR.
Canine parvovirus (CPV) and
feline panleukopenia virus (FPV) are important pathogens of dogs and
cats. CPV is a new virus of dogs that first appeared in 1978, having
arisen as a variant of a virus that infected cats or a related
carnivore (31). CPV and FPV are over 99% identical in DNA
sequence, but they differ in host range (29, 30). Both
viruses can infect feline and mink cells in tissue culture, but only
CPV can efficiently infect cultured canine cells (30). FPV
infection of dogs is restricted to certain cells of the bone marrow and
thymus (30). The molecular determinants of CPV host range
have been mapped to three regions on the surface of the capsid
structure. Single amino acid changes in these regions lead to loss of
the ability of CPV to infect canine, but not feline, cells (8,
19). Mutation of residues Asn93 During natural infections, CPV and FPV infect actively dividing cells
of the lymphopoietic system and the crypt cells of the intestine
(reviewed in reference 22). Initial virus replication occurs in the oropharyngeal lymphoid tissue, and the virus then spreads
hematogenously to other lymphoid organs and the intestine. Autonomous
parvoviruses (including CPV and FPV) can replicate only in mitotically
active cells during the S phase of the cell cycle (9), and
so the target organs in vivo are those that contain actively dividing
cell populations.
The pathway of viral entry into cells is only partially characterized.
Both CPV and FPV can bind sialic acid on the surface of some host
cells. However, binding sialic acid does not appear important for viral
infection, as mutants unable to bind sialic acid retain infectivity
(3). CPV capsids bound a 40- to 42-kDa protein when
overlaid on protein blots prepared from canine cell lysates
(5), but that protein has not been further characterized. CPV and FPV can infect feline and mink cells, indicating that they
likely share a common receptor and infection pathway in those cells.
The process of capsid uptake involves clathrin-mediated endocytosis,
and in feline or mink cells, capsids colocalize with transferrin in a
perinuclear compartment (20). Once endocytosed into cells,
capsids appear to penetrate only slowly into the cytoplasm. Anticapsid
antibodies injected into the cytoplasm of cells prevent virus infection
even 6 h after virus inoculation, suggesting that capsids still
remain within endocytic compartments several hours after uptake
(32).
We report that CPV and FPV bind to the human and feline transferrin
receptors (TfRs) and use those receptors to enter and infect cells.
Microinjected or exogenously added antibodies against the TfR prevented
viral infection of cells. CPV and FPV did not bind, enter, or infect
TfR-negative Chinese hamster ovary cells (TRVb cells), but they did
bind, enter, and infect TRVb-1 cells which express the human TfR and
TRVb cells transfected with the cDNA of the feline TfR. In feline-mouse
hybrid cells, the feline TfR gene locus (TFRC) was mapped to feline
chromosome C2 along with susceptibility to FPV infection.
Cells and viruses.
Feline CRFK and Norden Laboratories
feline kidney (NLFK) cells were grown in a 1:1 mixture of McCoy's 5A
and Leibovitz L15 media with 5% fetal bovine serum. Quail QT35 cells
were grown in M-24 medium with 4% chicken serum. HeLa cells were grown
in Dulbecco's modified Eagle medium with 10% fetal bovine serum. Chinese hamster ovary-derived TRVb and TRVb-1 cells (16)
were grown in Ham's F-12 medium with 10% fetal bovine serum, TRVb-1 cells being grown in the presence of 400 µg of Geneticin per ml.
0022-538X/01/$04.00+0 DOI: 10.1128/JVI.75.8.3896-3902.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Canine and Feline Parvoviruses Can Use Human or
Feline Transferrin Receptors To Bind, Enter, and Infect Cells


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ABSTRACT
Top
Abstract
Introduction
Materials and Methods
Results
Discussion
References
![]()
INTRODUCTION
Top
Abstract
Introduction
Materials and Methods
Results
Discussion
References
Asp and Asn323
Asp in the
VP2 capsid protein of FPV to the corresponding amino acids found in the
VP2 protein of CPV allows that mutant to infect dog cells
(8). The surface location of these host range determinants
suggests that host range may be determined by the ability to bind
a cell surface receptor or other cellular ligand (1).
![]()
MATERIALS AND METHODS
Top
Abstract
Introduction
Materials and Methods
Results
Discussion
References
Infection assays and antibody treatments. For all infections, a multiplicity of infection of ~1 was used. Infected cells were detected by immunostaining with a monoclonal antibody (MAb) against the nonstructural protein 1 (NS1) (36), followed by a goat anti-mouse immunoglobulin G (IgG)-Alexa 488 secondary conjugate (Molecular Probes, Eugene, Oreg.), or Texas Red-conjugated anti-NS1 IgG was used directly. Cells were fixed with 4% paraformaldehyde in phosphate-buffered saline (PBS) for 10 min and then permeabilized with 0.1% Triton X-100 in PBS with 1% bovine serum albumin (permeabilization buffer). All antibody incubations were carried out in permeabilization buffer for 45 min at room temperature.
To examine the effect of a polyclonal anti-human TfR on infection by CPV and FPV, HeLa or TRVb-1 cells were inoculated with CPV or FPV at a multiplicity of infection of 1, with titers being determined by 50% tissue culture infective dose assay in NLFK cells (19). A 1:500 dilution of sheep anti-human TfR (33) was added to the cells either at the time of virus inoculation or 2 h later and remained in the culture throughout the incubation. After 18 h of incubation at 37°C, the cells were fixed and permeabilized; infected cells were detected by staining with Texas Red-anti-NS1. The percentage of cells infected was compared to the average infection of untreated cells. To define the role of the feline TfR in virus infection and entry, antibody H68.4 (Zymed Laboratories Inc., South San Francisco, Calif.) against the cytoplasmic domain of the TfR (35) (anti-TfR-cyt) was injected into the cytoplasm of cells at various times around the time of virus inoculation. The H68.4 antibody was prepared against the human TfR and recognizes a peptide common to many species of TfRs, including the feline and canine receptors. Antibody 12CA5 IgG against an influenza virus hemagglutinin epitope was injected into control cells. The IgG antibodies were dialyzed against PBS, and then ~4 pl of antibody at 3 mg/ml was injected into CRFK cells either 2 h before or 4 or 7 h after inoculation with virus. The cells were then incubated for 24 h before fixing and staining for the viral NS1 protein as described above. To examine effects on capsid uptake, cells injected with anti-TfR-cyt or antihemagglutinin IgG were incubated for 2 h at 37°C and then incubated with 20 µg of CPV full capsids per ml in Dulbecco's modified Eagle medium with 1% bovine serum albumin for 2 h at 37°C. The cells were then washed in PBS, fixed in 4% paraformaldehyde in PBS, and permeabilized. The injected IgG was detected with goat anti-mouse IgG-Alexa 594 (Molecular Probes), while virus was detected with a rabbit polyclonal serum against intact CPV capsids followed by a goat anti-rabbit IgG-Alexa 488 conjugate (Molecular Probes).Cloning and expression of the TfR genes.
cDNA was prepared
from feline liver mRNA and used in a PCR to amplify the TfR gene in two
fragments using the Access reverse transcriptase PCR system (Promega,
Madison, Wis.). Gene-specific primer pairs ([i]
5'-TCTAGATTAAAACTCATTGTCAATATCCC-3' and
5'-CAGAAAAGGTTGCAAATGC-3'; [ii]
5'-ATATGGGTCACCTGTTCCCAGATGGGCAT-3' and
5'-CTCGAGGCCGCCACGGTGTGGCAGTTCAGAATGATGGAT-3') were used in
PCR. The intact cDNA was then cloned into the vector pcDNA3.1(
)
(Invitrogen, San Diego, Calif.) for expression. The gene sequence was
determined using automated sequencing.
Mapping virus susceptibility and the TfR gene in mouse-feline hybrid cells. Mouse × cat somatic hybrid cell lines that contain segregated feline chromosomes in different combinations (18) were inoculated with FPV at a multiplicity of infection of 0.1. Forty-eight hours later, low-molecular-weight DNA recovered from cells was tested for viral replicative-form DNA and single-stranded DNA by Southern blot analysis (8). The discordance between the presence of each feline chromosome and the cell susceptibility to FPV infection was calculated.
Radiation hybrid chromosomal mapping of the feline TfR gene (TFRC) was performed as described by Murphy et al. (17). Primers specific for the feline TfR gene were prepared (5'-CTGGCTCTCACACTCTGTCA-3' and 5'-CCCAAATGTCACCAGAGAGG-3'). DNA prepared from 93 clones of a feline-mouse 5,000-rad-radiation hybrid cell panel was tested using PCR for the presence or absence of the feline TfR gene. The results obtained allowed the gene to be positioned onto the C2 framework as described previously (17). The corresponding human chromosome 3 and chromosome 21 conserved segments were derived from the Genebridge-4-based maps in the Gene Map '99 radiation hybrid map database (www.ncbi.nlm.nih.gov/genemap).Nucleotide sequence accession number. The nucleotide sequence of the TfR gene was deposited in GenBank under accession no. AF276984.
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RESULTS |
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In preliminary studies, we observed that canine and mink cells
transiently overexpressing the human TfR appeared to bind and endocytose more CPV capsids than did control plasmid-transfected cells
or nontransfected cells (results not shown). Therefore, to examine the
role of the TfR in virus binding and uptake, we expressed the human TfR
or a control plasmid in quail QT35 cells. CPV capsids did not
detectably bind to or enter nontransfected QT35 cells or cells
transfected with a control plasmid, but they were bound to and taken up
to high levels in QT35 cells expressing the human TfR (Fig.
1A). In addition, CPV capsids did not
bind or enter TRVb cells, which do not express endogenous TfR, but they
efficiently bound to TRVb-1 cells that stably expressed the human TfR
(16) (Fig. 1B), as well as to human HeLa cells (data not
shown). The TRVb cells and both the nontransfected and human TfR-expressing QT35 cells were not susceptible to infection by CPV or
FPV (data not shown). In contrast, the human TfR-expressing TRVb-1
cells and HeLa cells were susceptible to infection by both CPV and FPV
(Fig. 2). Infection of TRVb-1 and HeLa
cells was blocked when antibodies against the human TfR were added to
those cells at the time of virus inoculation but not when the
antibodies were added 2 h later (Fig. 2).
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The anti-human TfR polyclonal serum did not recognize the feline TfR.
We therefore examined the effects of microinjection of an antibody
which recognized the cytoplasmic tail of the feline TfR (anti-TfR-cyt)
on CPV infection and uptake. Injecting anti-TfR-cyt into the cytoplasm
of feline CRFK cells 2 h before virus inoculation rendered them
almost completely resistant to CPV infection (Fig. 3A). In addition, the injected cells were
significantly less susceptible when the antibody was injected at 4 but
not 7 h after virus inoculation (Fig. 3A). The anti-TfR-cyt
injected 2 h prior to the virus inoculation did not prevent viral
endocytosis, but the virus-containing vesicles in the
anti-TfR-cyt-injected cells were larger and more widely dispersed
within the cytoplasm than were virus-containing vesicles in noninjected
cells (Fig. 3B). Injection of a control IgG had no effect on either
virus infection or the size and distribution of virus-containing
vesicles compared to those for noninjected cells (Fig. 3).
|
We inoculated feline-mouse hybrid cells that contain different known
combinations of feline chromosomes with FPV and examined the cells for
susceptibility to infection. The presence of feline chromosome C2 in a
hybrid cell correlated most closely with susceptibility to infection
(Fig. 4A). TFRC was mapped to a conserved
centromeric region of feline chromosome C2 by analysis of the DNA from
a 5,000-rad-radiation hybrid panel of 93 clones (Fig. 4B).
|
We cloned the feline TfR gene by reverse transcriptase PCR. The
translated sequence of the feline TfR cDNA was 80 and 76% identical to
the sequences of the human and Chinese hamster TfRs, respectively. CPV
and FPV capsids bound efficiently to TRVb cells expressing the feline
TfR but not to cells transfected with a control plasmid (Fig.
5A). To determine if the feline TfR would confer susceptibility on TRVb cells, we inoculated feline
TfR-transfected or vector control-transfected TRVb cells with CPV or
FPV. A high percentage of the feline TfR-expressing cells became
infected, while few infected cells were observed among cells
transfected with a control plasmid (Fig. 5B). We did not detect any
infected cells when nontransfected cells were inoculated.
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DISCUSSION |
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Our finding that CPV and FPV use the TfR to attach to and infect
cells is consistent with the current knowledge of the cellular infection pathway and of the pathogenesis of these viruses. We have
previously shown that CPV capsids enter cells by a dynamin-dependent, clathrin-mediated endocytic process and that they colocalize with human
transferrin in perinuclear vesicles of mink lung cells that express the
human TfR (20). In light of the findings reported here,
our previous observation of increased binding of CPV capsids to mink
lung cells overexpressing the Lys44
Ala (K44A) mutant of dynamin I
can be explained by increased numbers of TfRs on the cell surface, as
has been reported for the insulin receptor GLUT4 in cells
overexpressing dynamin K44A (12).
The TfR is a 90-kDa type II membrane protein that is expressed as a homodimer with an ~65- to 70-residue N-terminal cytoplasmic tail, a 20-residue transmembrane sequence, and an extracellular sequence of about 680 residues (27). Structures of the ectodomain show that it consists of apical, helical, and protease-like domains arranged in a "butterfly" configuration (14).
The TfR is constitutively endocytosed from the plasma membrane by clathrin-mediated endocytosis (13, 34). The natural function of the TfR is the cellular uptake of ferric iron bound to transferrin. The TfR-transferrin complex is delivered to the low-pH environment of the early endosome where ferric iron is released from transferrin. The iron-free transferrin remains bound to the receptor at low pH within endosomes until the complex is recycled to the cell surface, where the transferrin is released from the receptor at neutral pH, allowing iron-loaded transferrin to bind. As actively dividing cells require more iron than do nondividing cells, they express greater numbers of TfRs on their cell surface (26). Autonomous parvoviruses can replicate only in mitotically active cells during the S phase of cell cycle; they cannot induce cells to enter the cell cycle (9). Therefore, by binding the TfR, CPV and FPV can preferentially target actively dividing cells that will support viral DNA replication. High levels of TfR are found on small intestinal crypt cells and on actively dividing lymphoid cells, and both of these cell types are major targets for virus replication (2, 7, 15, 25).
Natural infection by CPV and FPV occurs via the oropharyngeal route, and initial viral replication occurs in the local oropharyngeal lymphoid tissue. Thereafter, these viruses spread to other organs hematogenously (reviewed in reference 22). The TfR is expressed mainly on the basolateral surface of polarized epithelial cells (10), and a previous study noted that CPV binds preferentially to the basolateral surface of polarized canine MDCK cells (4). Thus, the expression pattern of the TfR in epithelial cells correlates with the polarized binding of CPV and the hematogenous spread of these viruses to the intestinal epithelium during infection (22).
CPV and FPV did not bind, enter, or infect TfR-deficient TRVb cells. However, CPV and FPV did bind, enter, and infect TRVb-1 or HeLa cells, which express the human TfR on their surface, and infection of those cells was blocked by addition of a polyclonal antiserum against the human TfR at the time of virus inoculation. The TRVb and TRVb-1 cells are genetically identical except for the expression of the human TfR in TRVb-1 cells (16). Therefore, the TRVb cells possess all of the factors required for successful virus replication except the viral receptor. Control of virus host range and susceptibility at the level of the cell surface receptor has been reported for many viruses, including adenoviruses (6), coronaviruses (11), and picornaviruses (6). Although CPV and FPV bound and entered QT35 cells expressing the human TfR, they did not infect those cells (unpublished data), indicating that other factors required for the later stages of infection of mammalian cells differ in those avian cells.
MAb H68.4 (anti-TfR-cyt) binds the cytoplasmic tail of the feline TfR (35). When added to permeabilized cells, the H68.4 antibody blocked endocytosis but did not prevent formation of deep invaginations of the cell membrane that contained the TfR (23). In our studies, the microinjected anti-TfR-cyt antibodies efficiently blocked cell infection by CPV (Fig. 3A). Cells injected with anti-TfR-cyt still endocytosed capsids, but both the morphology and location of the virus-containing vesicles within the cytoplasm differed from those seen for noninjected or control-injected cells (Fig. 3B). The anti-TfR-cyt may interfere with the normal trafficking of viral capsids by masking portions of the cytoplasmic tail of the TfR that are required for trafficking or by cross-linking the receptors. Another possibility is that anti-TfR-cyt antibody binding to the cytoplasmic tail disrupts virus-receptor interactions required for infection which occur after the capsid has been removed from the cell surface and has entered the early endosome.
The animal host range of CPV and FPV appears to be naturally restricted to carnivores. Although the human TfR is used by CPV and FPV to infect TRVb-1 cells and human HeLa cells, there is no evidence that humans are infected by these viruses, and it is likely that many other host or viral factors prevent CPV or FPV from efficiently infecting and spreading between humans. The TfR appears to be a primary determinant of cell susceptibility to CPV and FPV infection of cat cells. Our preliminary studies show that the feline TfR can transfer FPV susceptibility to dog cells, indicating that the block to canine cell infection by FPV is likely due to the specific lack of a functional receptor. We are currently examining whether differences in the feline and canine TfRs determine virus susceptibility and the host range of these viruses.
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ACKNOWLEDGMENTS |
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S. C. Harrison, P. J. Bjorkmann, C. A. Enns, I. Mellman, and T. E. McGraw generously provided reagents and cell lines. We are grateful to J. F. Collawn for helpful discussions.
This work was supported by grants AI28385 and AI33468 from the National Institute of Allergy and Infectious Diseases to C.R.P. J.S.L.P. is supported by National Research Service Award F32 AI10134.
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FOOTNOTES |
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* Corresponding author. Mailing address: James A. Baker Institute, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853. Phone: (607) 256-5649. Fax: (607) 256-5608. E-mail: crp3{at}cornell.edu.
Present address: Department of Microbiology and Molecular Genetics,
Harvard Medical School, Boston, MA 02115.
Present address: Department of Molecular Biology, Princeton
University, Princeton, NJ 08544.
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REFERENCES |
|---|
|
|
|---|
| 1. | Agbandje, M., C. R. Parrish, and M. G. Rossmann. 1995. The structure of parvoviruses. Semin. Virol. 6:299-309[CrossRef]. |
| 2. | Anderson, G. J., L. W. Powell, and J. W. Halliday. 1990. Transferrin receptor distribution and regulation in the rat small intestine. Effect of iron stores and erythropoiesis. Gastroenterology 98:576-585[Medline]. |
| 3. | Barbis, D. P., S.-F. Chang, and C. R. Parrish. 1992. Mutations adjacent to the dimple of the canine parvovirus capsid structure affect sialic acid binding. Virology 191:301-308[CrossRef][Medline]. |
| 4. |
Basak, S., and R. W. Compans.
1989.
Polarized entry of canine parvovirus in an epithelial cell line.
J. Virol.
63:3164-3167 |
| 5. | Basak, S., H. Turner, and S. Parr. 1994. Identification of a 40- to 42-kDa attachment polypeptide for canine parvovirus in A72 cells. Virology 205:7-16[CrossRef][Medline]. |
| 6. |
Bergelson, J. M.,
A. Krithivas,
L. Celi,
G. Droguett,
M. S. Horwitz,
T. Wickham,
R. L. Crowell, and R. W. Finberg.
1998.
The murine CAR homolog is a receptor for coxsackie B viruses and adenoviruses.
J. Virol.
72:415-419 |
| 7. |
Chan, L. N., and E. M. Gerhardt.
1992.
Transferrin receptor gene is hyperexpressed and transcriptionally regulated in differentiating erythroid cells.
J. Biol. Chem.
267:8254-8259 |
| 8. |
Chang, S.-F.,
J.-Y. Sgro, and C. R. Parrish.
1992.
Multiple amino acids in the capsid structure of canine parvovirus coordinately determine the canine host range and specific antigenic and hemagglutination properties.
J. Virol.
66:6858-6867 |
| 9. | Cotmore, S. F., and P. Tattersall. 1987. The autonomously replicating parvoviruses of vertebrates. Adv. Virus Res. 33:91-174[Medline]. |
| 10. |
Fuller, S. D., and K. Simons.
1986.
Transferrin receptor polarity and recycling accuracy in "tight" and "leaky" strains of Madin-Darby canine kidney cells.
J. Cell Biol.
103:1767-1779 |
| 11. | Hensley, L. E., K. V. Holmes, N. Beauchemin, and R. S. Baric. 1998. Virus-receptor interactions and interspecies transfer of a mouse hepatitis virus. Adv. Exp. Med. Biol. 440:33-41[Medline]. |
| 12. |
Kao, A. W.,
B. P. Ceresa,
S. R. Santeler, and J. E. Pessin.
1998.
Expression of a dominant interfering dynamin mutant in 3T3L1 adipocytes inhibits GLUT4 endocytosis without affecting insulin signaling.
J. Biol. Chem.
273:25450-25457 |
| 13. | Larrick, J. W., C. Enns, A. Raubitschek, and H. Weintraub. 1985. Receptor-mediated endocytosis of human transferrin and its cell surface receptor. J. Cell. Physiol. 124:283-287[CrossRef][Medline]. |
| 14. |
Lawrence, C. M.,
S. Ray,
M. Babyonyshev,
R. Galluser,
D. W. Borhani, and S. C. Harrison.
1999.
Crystal structure of the ectodomain of human transferrin receptor.
Science
286:779-782 |
| 15. | Levine, D. S., and J. W. Woods. 1990. Immunolocalization of transferrin and transferrin receptor in mouse small intestinal absorptive cells. J. Histochem. Cytochem. 38:851-858[Abstract]. |
| 16. |
McGraw, T. E.,
L. Greenfield, and F. R. Maxfield.
1987.
Functional expression of the human transferrin receptor cDNA in Chinese hamster ovary cells deficient in endogenous transferrin receptor.
J. Cell Biol.
105:207-214 |
| 17. |
Murphy, W. J.,
S. Sun,
Z. Chen,
N. Yuhki,
D. Hirschmann,
M. Menotti-Raymond, and S. J. O'Brien.
2000.
A radiation hybrid map of the cat genome: implications for comparative mapping.
Genome Res.
10:691-702 |
| 18. |
O'Brien, S. J., and W. G. Nash.
1982.
Genetic mapping in mammals: chromosome map of domestic cat.
Science
216:257-265 |
| 19. | Parker, J. S. L., and C. R. Parrish. 1997. Canine parvovirus host range is determined by the specific conformation of an additional region of the capsid. J. Virol. 71:9214-9222[Abstract]. |
| 20. |
Parker, J. S. L., and C. R. Parrish.
2000.
Cellular uptake and infection by canine parvovirus involves rapid dynamin-regulated clathrin-mediated endocytosis, followed by slower intracellular trafficking.
J. Virol.
74:1919-1930 |
| 21. | Parrish, C. R. 1991. Mapping specific functions in the capsid structure of canine parvovirus and feline panleukopenia virus using infectious plasmid clones. Virology 183:195-205[CrossRef][Medline]. |
| 22. | Parrish, C. R. 1995. Pathogenesis of feline panleukopenia virus and canine parvovirus. Baillière's Clin. Haematol. 8:57-71[CrossRef][Medline]. |
| 23. |
Schmid, S. L., and E. Smythe.
1991.
Stage-specific assays for coated pit formation and coated vesicle budding in vitro.
J. Cell Biol.
114:869-880 |
| 24. |
Sheff, D. R.,
E. A. Daro,
M. Hull, and I. Mellman.
1999.
The receptor recycling pathway contains two distinct populations of early endosomes with different sorting functions.
J. Cell Biol.
145:123-139 |
| 25. | Testa, U., E. Pelosi, and C. Peschle. 1993. The transferrin receptor. Crit. Rev. Oncog. 4:241-276[Medline]. |
| 26. |
Trowbridge, I. S., and M. B. Omary.
1981.
Human cell surface glycoprotein related to cell proliferation is the receptor for transferrin.
Proc. Natl. Acad. Sci. USA
78:3039-3043 |
| 27. | Trowbridge, I. S., and D. A. Shackelford. 1986. Structure and function of transferrin receptors and their relationship to cell growth. Biochem. Soc. Symp. 51:117-129[Medline]. |
| 28. | Truyen, U., M. Agbandje, and C. R. Parrish. 1994. Characterization of the feline host range and a specific epitope of feline panleukopenia virus. Virology 200:494-503[CrossRef][Medline]. |
| 29. | Truyen, U., A. Gruenberg, S.-F. Chang, B. Obermaier, P. Veijalainen, and C. R. Parrish. 1995. Evolution of the feline-subgroup parvoviruses and the control of canine host range in vivo. J. Virol. 69:4702-4710[Abstract]. |
| 30. |
Truyen, U., and C. R. Parrish.
1992.
Canine and feline host ranges of canine parvovirus and feline panleukopenia virus: distinct host cell tropisms of each virus in vitro and in vivo.
J. Virol.
66:5399-5408 |
| 31. | Truyen, U., and C. R. Parrish. 1995. The evolution and control of parvovirus host ranges. Semin. Virol. 6:311-317. |
| 32. |
Vihinen-Ranta, M.,
W. Yuan, and C. R. Parrish.
2000.
Cytoplasmic trafficking of the canine parvovirus capsid and its role in infection and nuclear transport.
J. Virol.
74:4853-4859 |
| 33. |
Warren, R. A.,
F. A. Green, and C. A. Enns.
1997.
Saturation of the endocytic pathway for the transferrin receptor does not affect the endocytosis of the epidermal growth factor receptor.
J. Biol. Chem.
272:2116-2121 |
| 34. |
Watts, C.
1985.
Rapid endocytosis of the transferrin receptor in the absence of bound transferrin.
J. Cell Biol.
100:633-637 |
| 35. | White, S., K. Miller, C. Hopkins, and I. S. Trowbridge. 1992. Monoclonal antibodies against defined epitopes of the human transferrin receptor cytoplasmic tail. Biochim. Biophys. Acta 1136:28-34[Medline]. |
| 36. | Yeung, D. E., G. W. Brown, P. Tam, R. H. Russnak, G. Wilson, I. Clark-Lewis, and C. R. Astell. 1991. Monoclonal antibodies to the major nonstructural nuclear protein of minute virus of mice. Virology 181:35-45[CrossRef][Medline]. |
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