Human prion protein binds Argonaute and promotes accumulation of microRNA effector complexes

Abstract

Despite intense research in the context of neurodegenerative diseases associated with its misfolding, the endogenous human prion protein PrP(C) (or PRNP) has poorly understood physiological functions. Whereas most PrP(C) is exposed to the extracellular environment, conserved domains result in transmembrane forms of PrP(C) that traffic in the endolysosomal system and are linked to inherited and infectious neuropathologies. One transmembrane PrP(C) variant orients the N-terminal 'octarepeat' domain into the cytoplasm. Here we demonstrate that the octarepeat domain of human PrP(C) contains GW/WG motifs that bind Argonaute (AGO) proteins, the essential components of microRNA (miRNA)-induced silencing complexes (miRISCs). Transmembrane PrP(C) preferentially binds AGO, and PrP(C) promotes formation or stability of miRISC effector complexes containing the trinucleotide repeat-containing gene 6 proteins (TNRC6) and miRNA-repressed mRNA. Accordingly, effective repression of several miRNA targets requires PrP(C). We propose that dynamic interactions between PrP(C)-enriched endosomes and subcellular foci of AGO underpin these effects.

The Whereabouts of microRNA Actions: Cytoplasm and Beyond

“…As illustrated earlier for P-miRISC in Drosophila , the binding of AGO to Loqs-PB and GW182 is mutually exclusive [34], suggesting that altered compositions of miRISCs result in distinct functional consequences [4,11,35,36]. For example, AGO was recently shown to bind to the human prion protein PrP C [37]; this is the protein that, when misfolded, causes neurological pathologies, including variant Creutzfeldt–Jakob disease. PrP C co-fractionates with miRISC components on endosomes, including MVBs [27], and its binding to AGO promotes the formation or stability of GW182-containing miRISC [37].…”

“…For example, AGO was recently shown to bind to the human prion protein PrP C [37]; this is the protein that, when misfolded, causes neurological pathologies, including variant Creutzfeldt–Jakob disease. PrP C co-fractionates with miRISC components on endosomes, including MVBs [27], and its binding to AGO promotes the formation or stability of GW182-containing miRISC [37]. Alternatively, most AGO-bound miRNAs in adult tissues exist as low-molecular-weight complexes that are not associated with mRNA and GW182 [2]; these miRNAs are not actively engaged in target repression, but may act as miRNA reservoirs instead [2].…”

Autophagy supports genomic stability by degrading retrotransposon RNA

“…Cells were prepared for microscopy as previously described 4,43 . Cells were grown on 0.17-mm glass coverslips overnight before fixation in 2% paraformaldehyde in PBS (10 min).…”

RISC assembly: Coordination between small RNAs and Argonaute proteins

“…In flies and humans, AGO subfamily proteins are reported to localize at non-membranous bodies such as P-bodies and/or membranous organelles such as endoplasmic reticulum (ER), multivesicular bodies (MVBs) and Golgi [161][162][163][164][165][166][167][168][169][170][171][172][173][174][175][176][177][178][179][180].…”