anti--tubulin mouse monoclonal antibody ( sigma - aldrich corp ) , anti - arf6 mouse monoclonal antibody ( santa cruz biotechnology , inc ) , anti - rab11 rabbit polyclonal antibody , anti - tfr mouse monoclonal antibody ( invitrogen corp ) , anti - eea-1 mouse monoclonal antibody and anti - gm130 mouse monoclonal antibody ( bd biosciences ) were obtained commercially . s2 was performed with a fluorophore - conjugated anti - tfr antibody that was generated by using the zenon antibody labeling kit ( invitrogen corp ) . using this antibody slightly enhanced the tfr signals at the plasma membrane ( figs . s1 and s2 ) . all of the procedures used to perform cell culture , immunoblotting and the immunofluorescence analyses have been described elsewhere . anti--tubulin mouse monoclonal antibody ( sigma - aldrich corp ) , anti - arf6 mouse monoclonal antibody ( santa cruz biotechnology , inc ) , anti - rab11 rabbit polyclonal antibody , anti - tfr mouse monoclonal antibody ( invitrogen corp ) , anti - eea-1 mouse monoclonal antibody and anti - gm130 mouse monoclonal antibody ( bd biosciences ) were obtained commercially . s2 was performed with a fluorophore - conjugated anti - tfr antibody that was generated by using the zenon antibody labeling kit ( invitrogen corp ) . using this antibody slightly enhanced the tfr signals at the plasma membrane ( figs . s1 and s2 ) . all of the procedures used to perform cell culture , immunoblotting and the immunofluorescence analyses have been described elsewhere .