Application of Liquid-Liquid Extraction for N-terminal Myristoylation Proteomics

Cellular N-Myristoyl Transferases Are Required for Mammarenavirus Multiplication

The mammarenavirus matrix Z protein plays critical roles in virus assembly and cell egress. Meanwhile, heterotrimer complexes of a stable signal peptide (SSP) together with glycoprotein subunits GP1 and GP2, generated via co-and post-translational processing of the surface glycoprotein precursor GPC, form the spikes that decorate the virion surface and mediate virus cell entry via receptor-mediated endocytosis. The Z protein and the SSP undergo N-terminal myristoylation by host cell N-myristoyltransferases (NMT1 and NMT2), and G2A mutations that prevent myristoylation of Z or SSP have been shown to affect the Z-mediated virus budding and GP2-mediated fusion activity that is required to complete the virus cell entry process. In the present work, we present evidence that the validated on-target specific pan-NMT inhibitor DDD85646 exerts a potent antiviral activity against the prototypic mammarenavirus lymphocytic choriomeningitis virus (LCMV) that correlates with reduced Z budding activity and GP2-mediated fusion activity as well as with proteasome-mediated degradation of the Z protein. The potent anti-mammarenaviral activity of DDD85646 was also observed with the hemorrhagic-fever-causing Junin (JUNV) and Lassa (LASV) mammarenaviruses. Our results support the exploration of NMT inhibition as a broad-spectrum antiviral against human pathogenic mammarenaviruses.

Global analysis of N-myristoylation and its heterogeneity by combining N-terminomics and nanographite fluoride-based solid-phase extraction

N-myristoylation is one of the most widespread and important lipidation in eukaryotes and some prokaryotes, which is formed by covalently attaching various fatty acids (predominantly myristic acid C14:0) to the N-terminal glycine of proteins. Disorder of N-myristoylation is critically implicated in numerous physiological and pathological processes. Here, we presented a method for purification and comprehensive characterization of endogenous, intact N-glycine lipid-acylated peptides, which combined the negative selection method for N-terminome and the nanographite fluoride-based solid-phase extraction method (NeS-nGF SPE). After optimizing experimental conditions, we conducted the first global profiling of the endogenous and heterogeneous modification states for N-terminal glycine, pinpointing the precise sites and their associated lipid moieties. Totally, we obtained 76 N-glycine lipid-acylated peptides, including 51 peptides with myristate (C14:0), 10 with myristoleate (C14:1), 6 with tetradecadienoicate (C14:2), 5 with laurate (C12:0) and 4 with lauroleate (C12:1). Therefore, our proteomic methodology could significantly facilitate precise and in-depth analysis of the endogenous N-myristoylome and its heterogeneity.

Cellular N-myristoyl transferases Are Required for Mammarenavirus Multiplication

The mammarenavirus matrix Z protein plays critical roles in virus assembly and cell egress, whereas heterotrimer complexes of a stable signal peptide (SSP) together with glycoprotein subunits GP1 and GP2, generated via co-and post-translational processing of the surface glycoprotein precursor GPC, form the spikes that decorate the virion surface and mediate virus cell entry via receptor-mediated endocytosis. The Z protein and SSP undergo N-terminal myristoylation by host cell N-myristoyltransferases (NMT1 and NMT2), and G2A mutations that prevent myristoylation of Z or SSP have been shown to affect Z mediated virus budding and GP2 mediated fusion activity required to complete the virus cell entry process. In the present work, we present evidence that the validated on-target specific pan NMT inhibitor DDD85464 exerts a potent antiviral activity against the prototypic mammarenavirus lymphocytic choriomeningitis virus (LCMV) that correlated with reduced Z budding activity and GP2 mediated fusion activity, as well as proteasome mediated degradation of the Z protein. The potent anti-mammarenaviral activity of DDD85646 was also observed with the hemorrhagic fever causing mammarenaviruses Junin (JUNV) and Lassa (LASV) viruses. Our results support exploration of NMT inhibition as a broad-spectrum antiviral against human pathogenic mammarenaviruses.

Exploring protein lipidation by mass spectrometry-based proteomics

Protein lipidation is a common co- or post-translational modification that plays a crucial role in regulating the localization, interaction and function of cellular proteins. Dysregulation of lipid modifications can lead to various diseases, including cancer, neurodegenerative diseases and infectious diseases. Therefore, the identification of proteins undergoing lipidation and their lipidation sites should provide insights into many aspects of lipid biology, as well as providing potential targets for therapeutic strategies. Bottom-up proteomics using liquid chromatography/tandem mass spectrometry is a powerful technique for the global analysis of protein lipidation. Here, we review proteomic methods for profiling protein lipidation, focusing on the two major approaches: the use of chemical probes, such as lipid alkyne probes, and the use of enrichment techniques for endogenous lipid-modified peptides. The challenges facing these methods and the prospects for developing them further to achieve a comprehensive analysis of lipid modifications are discussed.