Structural Insights into allosteric inhibition of HRI kinase by heme binding via HDX-MS

TY - JOUR

T1 - Structural Insights into allosteric inhibition of HRI kinase by heme binding via HDX-MS

AU - Kanta, Shivani

AU - Vinciauskaite, Vanesa

AU - Neill, Graham

AU - Muqit, Miratul

AU - Masson, Glenn

PY - 2025/6

Y1 - 2025/6

N2 - Heme-regulated inhibitor (HRI) is one of the four mammalian kinases that phosphorylate eIF2α, facilitating a cellular response to stress through the regulation of mRNA translation. Originally identified as a heme sensor in erythroid progenitor cells, HRI has since emerged as a potential therapeutic target in both cancer and neurodegeneration. Here, we characterise two modes of HRI inhibition using structural mass spectrometry, biochemistry, and biophysics. We examined several competitive ATP-mimetic inhibitors – dabrafenib, encorafenib, and GCN2iB – and compared them with the heme-mimetic allosteric inhibitor, hemin. By combining hydrogen–deuterium exchange mass spectrometry with protein models generated by AlphaFold 3, we investigated the structural basis of inhibition by dabrafenib and hemin. Our analysis revealed that hemin inhibition induces large-scale structural rearrangements in HRI, which are not observed with ATP-mimetic inhibitors. Our results suggest that HRI may be inhibited using two distinctly different modalities, which may guide future drug development.

AB - Heme-regulated inhibitor (HRI) is one of the four mammalian kinases that phosphorylate eIF2α, facilitating a cellular response to stress through the regulation of mRNA translation. Originally identified as a heme sensor in erythroid progenitor cells, HRI has since emerged as a potential therapeutic target in both cancer and neurodegeneration. Here, we characterise two modes of HRI inhibition using structural mass spectrometry, biochemistry, and biophysics. We examined several competitive ATP-mimetic inhibitors – dabrafenib, encorafenib, and GCN2iB – and compared them with the heme-mimetic allosteric inhibitor, hemin. By combining hydrogen–deuterium exchange mass spectrometry with protein models generated by AlphaFold 3, we investigated the structural basis of inhibition by dabrafenib and hemin. Our analysis revealed that hemin inhibition induces large-scale structural rearrangements in HRI, which are not observed with ATP-mimetic inhibitors. Our results suggest that HRI may be inhibited using two distinctly different modalities, which may guide future drug development.

U2 - 10.1042/BCJ20253072

DO - 10.1042/BCJ20253072

M3 - Article

C2 - 40471279

SN - 0264-6021

VL - 482

SP - 859

EP - 875

JO - Biochemical Journal

JF - Biochemical Journal

IS - 12

ER -