Frontiers in Molecular Biosciences (Dec 2022)

Heterogeneous nuclear ribonucleoprotein hnRNPA2/B1 regulates the abundance of the copper-transporter ATP7A in an isoform-dependent manner

  • Courtney J. McCann,
  • Courtney J. McCann,
  • Nesrin M. Hasan,
  • Teresita Padilla-Benavides,
  • Shubhrajit Roy,
  • Svetlana Lutsenko

DOI
https://doi.org/10.3389/fmolb.2022.1067490
Journal volume & issue
Vol. 9

Abstract

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Copper (Cu) is an essential micronutrient with a critical role in mammalian growth and development. Imbalance of Cu causes severe diseases in humans; therefore, cellular Cu levels are tightly regulated. Major Cu-transport proteins and their cellular behavior have been characterized in detail, whereas their regulation at the mRNA level and associated factors are not well-understood. We show that the heterogeneous nuclear ribonucleoprotein hnRNPA2/B1 regulates Cu homeostasis by modulating the abundance of Cu(I)-transporter ATP7A. Downregulation of hnRNPA2/B1 in HeLa cells increases the ATP7A mRNA and protein levels and significantly decreases cellular Cu; this regulation involves the 3′ UTR of ATP7A transcript. Downregulation of B1 and B1b isoforms of hnRNPA2/B1 is sufficient to elevate ATP7A, whereas overexpression of either hnRNPA2 or hnRNPB1 isoforms decreases the ATP7A mRNA levels. Concurrent decrease in hnRNPA2/B1, increase in ATP7A, and a decrease in Cu levels was observed in neuroblastoma SH-SY5Y cells during retinoic acid-induced differentiation; this effect was reversed by overexpression of B1/B1b isoforms. We conclude that hnRNPA2/B1 is a new isoform-specific negative regulator of ATP7A abundance.

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