Heme binding causes structural rearrangements in HRI to inhibit activation via autophosphorylation

TY - UNPB

T1 - Heme binding causes structural rearrangements in HRI to inhibit activation via autophosphorylation

AU - Kanta, Shivani

AU - Vinciauskaite, Vanesa

AU - Neill, Graham

AU - Muqit, Miratul M.K.

AU - Masson, Glenn R

PY - 2024/8/14

Y1 - 2024/8/14

N2 - Heme-Regulated Inhibitor (HRI) is one of the four mammalian kinases which phosphorylates eIF2α to facilitate a cellular response to stress through the regulation of mRNA translation. Originally identified for its role as a heme sensor in erythroid progenitor cells, it has since materialised as a potential therapeutic target in both cancer and neurodegeneration. Here we characterise two modes of inhibition of HRI using structural mass spectrometry, biochemistry and biophysics. We demonstrate that several ATP-mimetic compounds, including BRAF inhibitors and a compound, GCN2iB, thought to be specific to GCN2, are capable of potently inhibiting HRI. We demonstrate that hemin, a haem-like molecule, inactivates HRI structurally using hydrogen-deuterium exchange mass spectrometry (HDX-MS), and this results in wide-spread structural rearrangement of the protein and how that impacts on the kinase domain through a series of allosteric interactions. This inhibition mainly impacts autophosphorylation, which includes tyrosine phosphorylation, not observed before in the eIF2α kinases.

AB - Heme-Regulated Inhibitor (HRI) is one of the four mammalian kinases which phosphorylates eIF2α to facilitate a cellular response to stress through the regulation of mRNA translation. Originally identified for its role as a heme sensor in erythroid progenitor cells, it has since materialised as a potential therapeutic target in both cancer and neurodegeneration. Here we characterise two modes of inhibition of HRI using structural mass spectrometry, biochemistry and biophysics. We demonstrate that several ATP-mimetic compounds, including BRAF inhibitors and a compound, GCN2iB, thought to be specific to GCN2, are capable of potently inhibiting HRI. We demonstrate that hemin, a haem-like molecule, inactivates HRI structurally using hydrogen-deuterium exchange mass spectrometry (HDX-MS), and this results in wide-spread structural rearrangement of the protein and how that impacts on the kinase domain through a series of allosteric interactions. This inhibition mainly impacts autophosphorylation, which includes tyrosine phosphorylation, not observed before in the eIF2α kinases.

U2 - 10.1101/2024.08.14.607626

DO - 10.1101/2024.08.14.607626

M3 - Preprint

BT - Heme binding causes structural rearrangements in HRI to inhibit activation via autophosphorylation

PB - BioRxiv

ER -