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Coexpression and association of the spike protein and the membrane protein of mouse hepatitis virus
D J Opstelten1, M J Raamsman, K Wolfs
1Department of Infectious Diseases and Immunology, Faculty of Veterinary Medicine, Utrecht University, The Netherlands.
Abstract:
The M and S envelope glycoproteins of mouse hepatitis virus associate in the process of virus assembly. We have studied the intrinsic properties of M/S heterocomplexes by coexpressing M and S in the absence of other coronaviral proteins. The formation of M/S complexes under these conditions indicates that M and S can interact independently of other coronaviral factors. Pulse-chase analysis revealed that M and S associate in a pre-Golgi compartment. M/S complexes are efficiently transported beyond the coronavirus budding compartment to the Golgi complex. The failure to detect complexes at the surface of coexpressing cells demonstrated that they are retained intracellularly. Thus, coexpression of the envelope glycoproteins drastically affects the intracellular transport of the S protein: instead of being transported to the cell surface, S is retained intracellularly by its association with M.
Insights
Mouse hepatitis virus M and S envelope glycoproteins form complexes independently. These M/S complexes associate in a pre-Golgi compartment and are retained intracellularly, affecting S protein transport.
Area of Science:
- Virology
- Molecular Biology
- Cell Biology
Background:
- Mouse hepatitis virus (MHV) assembly involves interactions between its M and S envelope glycoproteins.
- Understanding these interactions is crucial for deciphering coronavirus assembly and pathogenesis.
Purpose of the Study:
- To investigate the intrinsic properties of M/S heterocomplexes.
- To determine if M and S glycoproteins can associate independently of other viral proteins.
- To elucidate the intracellular transport pathway of M/S complexes.
Main Methods:
- Coexpression of M and S envelope glycoproteins in the absence of other viral proteins.
- Pulse-chase analysis to track protein association and transport.
- Cell surface expression analysis.
Main Results:
- M and S glycoproteins form stable heterocomplexes even without other viral factors.
- M/S complex formation occurs in a pre-Golgi compartment.
- M/S complexes are transported to the Golgi complex but are retained intracellularly, not reaching the cell surface.
- The association with M protein retains the S protein intracellularly.
Conclusions:
- The M and S envelope glycoproteins of mouse hepatitis virus possess intrinsic properties allowing them to interact and form stable complexes.
- These M/S complexes follow a specific intracellular trafficking pathway, associating early in the secretory pathway (pre-Golgi).
- The intracellular retention of M/S complexes significantly impacts the transport of the S protein, preventing its surface expression.