Host lipids required for Membrane protein matrix formation in new severe acute respiratory syndrome-related coronavirus (SARS-CoV-2), ribonucleocapsid packaging and viral assembly.

The current model of SARS-CoV-2 assembly proposes a multistage process: (i) the viral RNA coated with the nucleoprotein (N) forms the ribonucleoprotein (RNP), (ii) traffics to the endoplasmic reticulum-Golgi apparatus intermediate compartment (ERGIC)-derived vesicles to (iii) interact with the membrane (M) assembled along with spike (S) and envelope (E) proteins. Coronaviruses' M has been described as required for new virus particle assembly. To date, biochemical and structural information on M are unavailable and key host factors required for M lattice formation, trafficking and interaction with the RNP are poorly characterized. The objective of this research project is to progress our understanding of SARS-CoV-2 assembly. Our central hypothesis is that M through its interaction with host lipids coordinates viral protein interactions and RNP packaging as key processes for SARS-CoV-2 assembly and spread. The role of lipids as molecules regulating the viral life cycle is poorly investigated. Our current data demonstrates a clear binding of cell expressed M to a Golgi resident sphingolipid. Furthermore, mutations at the sphingolipid binding motif resulted in deficient pull down of M protein by sphingolipid coated beads. In cells, the M sphingolipid-binding mutant failed to retain S protein at viral assembly membranes resulting in a reduced entry capacity of newly formed virus-like particles. Our current study is providing a first insight on the direct role of host lipids during SARS-CoV-2 assembly, orchestrated by the M protein.