A novel virus- and integrin clustering–specific pathway diverts integrin from its normal endo/exocytic traffic to a nonrecycling degradative endosomal route. Clustering of α2β1 integrin causes redistribution of the integrin to perinuclear endosomes, leading to enhanced integrin turnover promoted by calpains.

SummaryNon-enveloped picornavirus echovirus 1 (EV1) clusters its receptor a2b1 integrin and causes their internalization and accumulation in a2b1 integrin enriched multivesicular bodies (a2-MVBs). Our results here show that these a2-MVBs are distinct from acidic late endosomes/lysosomes by several criteria: (i) live intra-endosomal pH measurements show that a2-MVBs are not acidic, (ii) they are not positive for the late endosomal marker LBPA or Dil-LDL internalized to lysosomes, and (iii) simultaneous stimulation of epidermal growth factor receptor (EGFR) and a2b1 integrin clustering leads to their accumulation in separate endosomes. EGFR showed downregulation between 15 min and 2 h, whereas accumulation of a2b1 integrin/EV1 led to an increase of integrin fluorescence in cytoplasmic vesicles further suggesting that EV1 pathway is separate from the lysosomal downregulation pathway. In addition, the results demonstrate the involvement of ESCRTs in the biogenesis of a2-MVBs. Overexpression of dominant-negative form of VPS4 inhibited biogenesis of a2-MVBs and efficiently prevented EV1 infection. Furthermore, a2-MVBs were positive for some members of ESCRTs such as Hrs, VPS37A and VPS24 and the siRNA treatment of TSG101, VPS37A and VPS24 inhibited EV1 infection. Our results show that the non-enveloped EV1 depends on biogenesis of novel multivesicular structures for successful infection.