This study investigates how feline calicivirus (FCV) initiates viral replication by examining three non-structural proteins: p32, p39, and p30. Using bioinformatics and cell biology techniques, the researchers demonstrated that these proteins are integral membrane proteins that localize to the endoplasmic reticulum (ER). When expressed in cells, p39 and p30 caused significant reorganization of ER membranes, including dilation and formation of fenestrated networks. Similar ER remodeling was observed in naturally infected feline kidney cells. The proteins affected ER homeostasis by reducing accumulation of an ER-resident marker protein, suggesting disruption of normal ER function. Electron microscopy revealed that p30 expression generated large membrane stacks and polarized ER networks, while p39 caused extensive ER dilation. The data indicate that these viral proteins likely play critical roles in generating membrane-bound replication complexes on the ER, providing insight into how FCV establishes the cellular environment necessary for viral RNA replication.

Key findings

• FCV non-structural proteins p32, p39, and p30 are integral membrane proteins that localize to the endoplasmic reticulum
• Expression of p30 and p39 causes substantial reorganization of ER membranes, including formation of fenestrated networks and membrane stacks
• These viral proteins disrupt ER homeostasis by reducing accumulation of ER-resident proteins, indicating interference with normal cellular trafficking pathways
• The data suggest the ER serves as the membrane source for FCV replication complex formation, distinct from picornavirus mechanisms