Role of sialic acid-containing molecules and the alpha4beta1 integrin receptor in the early steps of polyomavirus infection.
Murine polyomavirus (MPyV) infection occurs through recognition of sialic acid (SA) residues present on the host cell membrane, but the nature of the molecules involved and the exact role of this interaction in virus cell entry still need to be clarified. In this work, mutations at residues R(77) or H(298) of the MPyV VP1 protein were shown to lead to a complete loss of virus infectivity, which, however, could be restored by lipofection of virus particles into the cytoplasm of the host cells. Using virus-like particles (VLPs), it was demonstrated that the non-infectivity of these mutants was due to impaired cell entry caused by total abrogation of SA-dependent cell binding. This indicates that SA residues are essential primary cell receptors for MPyV. As the alpha4beta1 integrin has been identified recently as a cell receptor for MPyV, the relationship, if any, was investigated between SA-containing and alpha4beta1 integrin receptors. The ability of mutants R(77)Q and H(298)Q and wt VLPs to bind to cells overexpressing the alpha4beta1 integrin was studied in SA-positive (BALB/c 3T3 cells and Pro-5 cells) and SA-deficient (Pro5-derived Lec-2 cells) backgrounds. Overexpression of alpha4beta1 integrin did not restore binding of mutant VLPs in any of these cell lines or, indeed, that of wt VLPs in a SA-deficient background. Moreover, evidence is provided that overexpression of the sialylated alpha4beta1 integrin enhances wt VLP cell binding, suggesting that, in addition to its function at a post-attachment level, alpha4beta1 integrin acts also as one of the SA-containing receptors for initial cell binding.
Istituto Pasteur-Fondazione Cenci Bolognetti, Dipartimento di Biotecnologie Cellulari ed Ematologia, Sezione di Genetica Molecolare, Università di Roma 'La Sapienza', Viale Regina Elena 324, 00161 Rome, Italy.
Maddalena
M
Caruso
Istituto Pasteur-Fondazione Cenci Bolognetti, Dipartimento di Biotecnologie Cellulari ed Ematologia, Sezione di Genetica Molecolare, Università di Roma 'La Sapienza', Viale Regina Elena 324, 00161 Rome, Italy.
Michaela
M
Cavaldesi
e Dipartimento di Medicina Sperimentale e Patologia, Sezione di Virologia, Università di Roma 'La Sapienza', Viale Regina Elena 324, 00161 Rome, Italy.
Massimo
M
Gentile
Istituto Pasteur-Fondazione Cenci Bolognetti, Dipartimento di Biotecnologie Cellulari ed Ematologia, Sezione di Genetica Molecolare, Università di Roma 'La Sapienza', Viale Regina Elena 324, 00161 Rome, Italy.
Olga
O
Sthandier
Istituto Pasteur-Fondazione Cenci Bolognetti, Dipartimento di Biotecnologie Cellulari ed Ematologia, Sezione di Genetica Molecolare, Università di Roma 'La Sapienza', Viale Regina Elena 324, 00161 Rome, Italy.
Paolo
P
Amati
Istituto Pasteur-Fondazione Cenci Bolognetti, Dipartimento di Biotecnologie Cellulari ed Ematologia, Sezione di Genetica Molecolare, Università di Roma 'La Sapienza', Viale Regina Elena 324, 00161 Rome, Italy.
Marie-Isabelle
MI
Garcia
D016475:3T3 Cells; D000818:Animals; D036022:Capsid Proteins / Q000378:metabolism; D005347:Fibroblasts / Q000821:virology; D039041:Integrin alpha4beta1 / Q000502:physiology*; D051379:Mice; D027601:Polyomavirus Infections / Q000209:etiology*; D012367:RNA, Viral / Q000032:analysis; D012794:Sialic Acids / Q000378:metabolism*; D014771:Virion / Q000502:physiology
D036022:Capsid Proteins; D039041:Integrin alpha4beta1; D012367:RNA, Viral; D012794:Sialic Acids