The molecular chaperone gp96/GRP94 interacts with Toll-like receptors and integrins via its C-terminal hydrophobic domain.
The structural basis for molecular chaperones to discern misfolded proteins has long been an enigma. As the endoplasmic reticulum paralogue of the cytosolic HSP90, gp96 (GRP94, HSP90b1) is an essential molecular chaperone for Toll-like receptors (TLRs) and integrins. However, little is known about its client-binding domain (CBD). Herein, we provide genetic and biochemical evidence to definitively demonstrate that a C-terminal loop structure, formed by residues 652-678, is the critical region of CBD for both TLRs and integrins. Deletion of this region affects neither the intrinsic ATPase activity nor the overall conformation of gp96. However, without it, the chaperoning function of gp96 collapses. We also find a critical Met pair (Met(658)-Met(662)) for the folding of integrins but not TLRs. Moreover, we find that the TLR binding to gp96 is also dependent on the C-terminal dimerization domain but not the N-terminal ATP-binding pocket of gp96. Our study has unveiled surprisingly the exquisite specificity of gp96 in substrate binding and suggests a manipulation of its CBD as an alternative strategy for targeted therapy of a variety of diseases.
Department of Immunology, MC 1601, University of Connecticut School of Medicine, Farmington, Connecticut 06030-1601, USA.
Shuang
S
Wu
Feng
F
Hong
Daniel
D
Gewirth
Beichu
B
Guo
Bei
B
Liu
Zihai
Z
Li
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002460:Cell Line; D019281:Dimerization; D004721:Endoplasmic Reticulum / Q000378:metabolism; D017353:Gene Deletion; D018841:HSP90 Heat-Shock Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D057927:Hydrophobic and Hydrophilic Interactions; D007113:Immunity, Innate / Q000502:physiology; D016023:Integrins / Q000378:metabolism*; D008715:Methionine / Q000737:chemistry; D051379:Mice; D018832:Molecular Chaperones / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D054448:Precursor Cells, B-Lymphoid / Q000166:cytology / Q000502:physiology; D017434:Protein Structure, Tertiary; D051193:Toll-Like Receptors / Q000378:metabolism*; D056811:Unfolded Protein Response / Q000502:physiology
D018841:HSP90 Heat-Shock Proteins; C490097:Hsp90b1 protein, mouse; D016023:Integrins; D018832:Molecular Chaperones; D051193:Toll-Like Receptors; D000255:Adenosine Triphosphate; D008715:Methionine