Biophysical approaches to the study of heteromeric amyloid fibrils involved in viral inhibition of necroptosis

Pham CLL1, Strange M1, O'Carroll A2, Shanmugam N1, Sierecki E2, Gambin Y2, Steain M3 and Sunde M1

  1. Discipline of Pharmacology, School of Medical Sciences and Sydney Nano, University of Sydney, NSW 2006, Australia.
  2. EMBL Australia Node in Single Molecule Sciences, School of Medical Science, University of New South Wales, NSW 2052, Australia.
  3. Infectious Diseases and Immunology, Central Clinical School, Sydney Medical School, University of Sydney, NSW 2006, Australia.

The large DNA viruses, cytomegalovirus and herpes simplex virus, express proteins that inhibit the host necroptosis programmed cell death pathway. Our recent studies show that the RIP homotypic interaction motif (RHIM) within the viral necroptosis inhibitor proteins renders them amyloidogenic. The viral proteins are therefore functional amyloid structures, in which the biologically active form of the protein is retained or generated in the self-assembled fibrillar form of the protein. We have used a wide range of biophysical techniques, including single molecule fluorescence studies, to investigate the fibrils formed by these proteins. We have demonstrated that these proteins are able to form heteromeric amyloid fibrils through co-assembly with host proteins, RIPK1, RIPK3 and ZBP1/DAI, which each contain RHIMs. Incorporation of viral proteins into host amyloid fibrils alters the structure and properties of the fibrils and renders the component proteins unable to signal for cell death.