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Role of the mu 1 protein in reovirus stability and capacity to cause chromium release from host cells.

ABSTRACT: The reovirus M2 gene is associated with the capacity of type 3 strain Abney (T3A) intermediate subviral particles (ISVPs) to permeabilize cell membranes as measured by chromium (51Cr) release (P. Lucia-Jandris, J. W. Hooper, and B. N. Fields, J. Virol. 67:5339-5345, 1993). In addition, reovirus mutants with lesions in the M2 gene can be selected by heating virus at 37 degrees C for 20 min in 33% ethanol (D. R. Wessner and B. N. Fields, J. Virol. 67:2442-2447, 1993). In this report we investigated the mechanism by which the reovirus M2 gene product (the mu 1 protein) influences the capacity of reovirus ISVPs to permeabilize membranes, using ethanol-selected T3A mutants. Each of three T3A ethanol-resistant mutants isolated (JH2, JH3, and JH4) exhibited a decreased capacity to cause 51Cr release relative to that of wild-type T3A. Sequence analysis of the M2 genes of wild-type T3A and the T3A mutants indicated that each mutant possesses a single amino acid substitution in a central region of the 708-amino-acid mu 1 protein: JH2 (residue 466, Tyr to Cys), JH3 (residue 459, Lys to Glu), and JH4 (residue 497 Pro to Ser). Assays performed with reovirus natural isolates, reassortants, and a set of previously characterized type 3 strain Dearing (T3D) ethanol-resistant mutants revealed a strong correlation between ethanol sensitivity and the capacity to cause 51Cr release. We found that ISVPs generated from the T3A and T3D mutants were stable when heated to 50 degrees C, whereas wild-type T3A ISVPs are inactivated under these conditions. Together, these data suggest that amino acid substitutions in a central region of the mu 1 protein affect the capacity of the ISVP to permeabilize L-cell membranes by altering the stability of the virus particle.

SUBMITTER: Hooper JW

PROVIDER: S-EPMC189834 | biostudies-other | 1996 Jan

REPOSITORIES: biostudies-other

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Role of the mu 1 protein in reovirus stability and capacity to cause chromium release from host cells.

Hooper J W JW Fields B N BN

Journal of virology 19960101 1

The reovirus M2 gene is associated with the capacity of type 3 strain Abney (T3A) intermediate subviral particles (ISVPs) to permeabilize cell membranes as measured by chromium (51Cr) release (P. Lucia-Jandris, J. W. Hooper, and B. N. Fields, J. Virol. 67:5339-5345, 1993). In addition, reovirus mutants with lesions in the M2 gene can be selected by heating virus at 37 degrees C for 20 min in 33% ethanol (D. R. Wessner and B. N. Fields, J. Virol. 67:2442-2447, 1993). In this report we investigate ...[more]

PMID: 8523558

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Project description:The mammalian orthoreovirus (reovirus) outer capsid is composed of 200 ?1-?3 heterohexamers and a maximum of 12 ?1 trimers. During cell entry, ?3 is degraded by luminal or intracellular proteases to generate the infectious subviral particle (ISVP). When ISVP formation is prevented, reovirus fails to establish a productive infection, suggesting proteolytic priming is required for entry. ISVPs are then converted to ISVP*s, which is accompanied by ?1 rearrangements. The ?1 and ?3 proteins confer resistance to inactivating agents; however, neither the impact on capsid properties nor the mechanism (or basis) of inactivation is fully understood. Here, we utilized T1L/T3D M2 and T3D/T1L S4 to investigate the determinants of reovirus stability. Both reassortants encode mismatched subunits. When ?1-?3 were derived from different strains, virions resembled wild-type particles in structure and protease sensitivity. T1L/T3D M2 and T3D/T1L S4 ISVPs were less thermostable than wild-type ISVPs. In contrast, virions were equally susceptible to heating. Virion associated ?1 adopted an ISVP*-like conformation concurrent with inactivation; ?3 preserves infectivity by preventing ?1 rearrangements. Moreover, thermostability was enhanced by a hyperstable variant of ?1. Unlike the outer capsid, the inner capsid (core) was highly resistant to elevated temperatures. The dual layered architecture allowed for differential sensitivity to inactivating agents.IMPORTANCE Nonenveloped and enveloped viruses are exposed to the environment during transmission to a new host. Protein-protein and/or protein-lipid interactions stabilize the particle and protect the viral genome. Mammalian orthoreovirus (reovirus) is composed of two concentric, protein shells. The ?1 and ?3 proteins form the outer capsid; contacts between neighboring subunits are thought to confer resistance to inactivating agents. We further investigated the determinants of reovirus stability. The outer capsid was disrupted concurrent with the loss of infectivity; virion associated ?1 rearranged into an altered conformation. Heat sensitivity was controlled by ?3; however, particle integrity was enhanced by a single ?1 mutation. In contrast, the inner capsid (core) displayed superior resistance to heating. These findings reveal structural components that differentially contribute to reovirus stability.

Dataset Information

Role of the mu 1 protein in reovirus stability and capacity to cause chromium release from host cells.

Publications

Role of the mu 1 protein in reovirus stability and capacity to cause chromium release from host cells.

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