atomic-scale-structural-studies-macromolecular-assemblies-solid-state

Atomic Scale Structural Studies of Macromolecular Assemblies by Solid-state Nuclear Magnetic Resonance Spectroscopy

Supramolecular protein assemblies play fundamental roles in biological processes ranging from host-pathogen interaction, viral infection to the ...

UMR5248 CNRS, Université de Bordeaux

Recent findings have revealed the role of prion-like mechanisms in the control of host defense and programmed cell death cascades. In fungi, HET-S, a cell death-inducing protein containing a HeLo pore-forming domain, is activated through amyloid templating by a Nod-like receptor (NLR). Here we characterize the HELLP protein behaving analogously to HET-S and bearing a new type of N-terminal cell death-inducing domain termed HeLo-like (HELL) and a C-terminal regulatory amyloid motif known as PP. The gene encoding HELLP is part of a three-gene cluster also encoding a lipase (SBP) and a Nod-like receptor, both of which display the PP motif. The PP motif is similar to the RHIM amyloid motif directing formation of the RIP1/RIP3 necrosome in humans. The C-terminal region of HELLP, HELLP(215-278), encompassing the motif, allows prion propagation and assembles into amyloid fibrils, as demonstrated by X-ray diffraction and FTIR analyses. Solid-state NMR studies reveal a well-ordered local structure of the amyloid core residues and a primary sequence that is almost entirely arranged in a rigid conformation, and confirm a β-sheet structure in an assigned stretch of three amino acids. HELLP is activated by amyloid templating and displays membrane-targeting and cell death-inducing activity. HELLP targets the SBP lipase to the membrane, suggesting a synergy between HELLP and SBP in membrane dismantling. Remarkably, the HeLo-like domain of HELLP is homologous to the pore-forming domain of MLKL, the cell death-execution protein in necroptosis, revealing a transkingdom evolutionary relationship between amyloid-controlled fungal programmed cell death and mammalian necroptosis.

Identification of a novel cell death-inducing domain reveals that fungal amyloid-controlled programmed cell death is related to necroptosis.

The receptor tyrosine kinase MET is essential to embryonic development and organ regeneration. Its deregulation is associated with tumorigenesis. While MET gene amplification and mutations leading to MET self-activation concern only a few patients, a high MET level has been found in about half of the non-small cell lung cancers (NSCLCs) tested. How this affects MET activation in tumors is unclear. Also uncertain is the prognostic value, in cancer, of a phenomenon well described in cell models: MET shedding, i.e. its cleavage by membrane proteases leading to release of a soluble fragment into the medium.

High-MET status in non-small cell lung tumors correlates with receptor phosphorylation but not with the serum level of soluble form.

We demonstrate sensitive detection of alpha protons of fully protonated proteins by solid-state NMR spectroscopy with 100-111 kHz magic-angle spinning (MAS). The excellent resolution in the Cα-Hα plane is demonstrated for 5 proteins, including microcrystals, a sedimented complex, a capsid and amyloid fibrils. A set of 3D spectra based on a Cα-Hα detection block was developed and applied for the sequence-specific backbone and aliphatic side-chain resonance assignment using only 500 μg of sample. These developments accelerate structural studies of biomolecular assemblies available in submilligram quantities without the need of protein deuteration.

NMR Spectroscopic Assignment of Backbone and Side-Chain Protons in Fully Protonated Proteins: Microcrystals, Sedimented Assemblies, and Amyloid Fibrils.

Article	Year
Identification of a novel cell death-inducing domain reveals that fungal amyloid-controlled programmed cell death is related to necroptosis. Proceedings of the National Academy of Sciences of the United States of America\| PubMed ID: 26903619	2016
High-MET status in non-small cell lung tumors correlates with receptor phosphorylation but not with the serum level of soluble form. Lung cancer (Amsterdam, Netherlands)\| PubMed ID: 27794409	2016
NMR Spectroscopic Assignment of Backbone and Side-Chain Protons in Fully Protonated Proteins: Microcrystals, Sedimented Assemblies, and Amyloid Fibrils. Angewandte Chemie (International ed. in English)\| PubMed ID: 27865050	2016

Melanie Berbon

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