 For example, the HIV-1 viroporin Vpu promotes viral budding through interactions with the CD4 receptor and tetherin, though the precise molecular mechanism of this interaction is not known.The JC polyomavirus agnoprotein functions as a viroporin in addition to other roles mediated through interactions with viral proteins such as major capsid protein VP1.Viroporins can also be considered virulence factors; in viruses in which viroporins are not essential, their pathogenicity is attenuated in the absence of viroporin beyond the level expected by the effects on viral propagation.