Crystal structure of EML1 reveals the basis for Hsp90 dependence of oncogenic EML4-ALK by disruption of an atypical β-propeller domain.
Proteins of the echinoderm microtubule-associated protein (EMAP)-like (EML) family contribute to formation of the mitotic spindle and interphase microtubule network. They contain a unique hydrophobic EML protein (HELP) motif and a variable number of WD40 repeats. Recurrent gene rearrangements in nonsmall cell lung cancer fuse EML4 to anaplastic lymphoma kinase (ALK), causing expression of several fusion oncoprotein variants. We have determined a 2.6-Å crystal structure of the representative ∼70-kDa core of EML1, revealing an intimately associated pair of β-propellers, which we term a TAPE (tandem atypical propeller in EMLs) domain. One propeller is highly atypical, having a discontinuous subdomain unrelated to a WD40 motif in place of one of its blades. This unexpected feature shows how a propeller structure can be assembled from subdomains with distinct folds. The HELP motif is not an independent domain but forms part of the hydrophobic core that joins the two β-propellers. The TAPE domain binds α/β-tubulin via its conserved, concave surface, including part of the atypical blade. Mapping the characteristic breakpoints of each EML4-ALK variant onto our structure indicates that the EML4 TAPE domain is truncated in many variants in a manner likely to make the fusion protein structurally unstable. We found that the heat shock protein 90 (Hsp90) inhibitor ganetespib induced degradation of these variants whereas others lacking a partial TAPE domain were resistant in both overexpression models and patient-derived cell lines. The Hsp90-sensitive EML4-ALK variants are exceptions to the rule that oncogenic fusion proteins involve breakpoints in disordered regions of both partners.
Department of Biochemistry, University of Leicester, Leicester LE1 9HN, United Kingdom.
Mark W
MW
Richards
Edward W P
EW
Law
La'Verne P
LP
Rennalls
Sara
S
Busacca
Laura
L
O'Regan
Andrew M
AM
Fry
Dean A
DA
Fennell
Richard
R
Bayliss
D000595:Amino Acid Sequence; D000077548:Anaplastic Lymphoma Kinase; D018797:Cell Cycle Proteins / Q000737:chemistry* / Q000378:metabolism; D018360:Crystallography, X-Ray; D018841:HSP90 Heat-Shock Proteins / Q000378:metabolism*; D006801:Humans; D008869:Microtubule-Associated Proteins / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D020794:Receptor Protein-Tyrosine Kinases / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D012697:Serine Endopeptidases / Q000737:chemistry* / Q000378:metabolism
D018797:Cell Cycle Proteins; D018841:HSP90 Heat-Shock Proteins; D008869:Microtubule-Associated Proteins; C000626173:ALK protein, human; D000077548:Anaplastic Lymphoma Kinase; D020794:Receptor Protein-Tyrosine Kinases; C415585:EML4 protein, human; D012697:Serine Endopeptidases
stratified medicine; structural biology