AMPK/ULK1 activation downregulates TXNIP, Rab5, and Rab7 and inhibits endocytosis-mediated entry of human pathogenic viruses

Abstract

AbstractCellular metabolism must adapt rapidly to environmental alterations and adjust nutrient uptake. Low glucose availability activates the AMP-dependent kinase (AMPK) pathway. We demonstrate that activation of AMPK or the downstream Unc-51-like autophagy-activating kinase (ULK1) inhibits receptor-mediated endocytosis. Beyond limiting dextran-uptake, this activation prevents endocytic uptake of human pathogenic enveloped and non-enveloped, positive and negative-stranded RNA viruses, such as yellow fever, dengue, tick-borne encephalitis, chikungunya, polio, rubella, rabies lyssavirus and SARS-CoV-2 not only in mammalian and insect cells but in precision-cut lung slices and neuronal organoids. However, receptor presentation at the cytoplasmic membrane was unaffected, indicating that receptor-binding remained unaltered and later steps of endocytosis were targeted. Indeed, AMPK pathway activation reduced early endocytic factors TXNIP, Rab5 and the late endosomal marker Rab7 amounts. Furthermore, AMPK activation impaired SARS-CoV-2 late-replication steps by reducing viral RNAs and proteins and the endo-lysosomal markers LAMP1 and GRP78, suggesting a reduction of early and late endosomes and lysosomes. Inhibition of the PI3K and mTORC2 pathways, which sense amino acids and growth factor availability, promotes AMPK activity and blocks viral entry. Our results indicate that AMPK and ULK1 emerge as restriction factors of cellular endocytosis, impeding the receptor-mediated endocytic entry of enveloped and non-enveloped RNA viruses.