Virulence protein that plays a central role in mammalian macrophage infection, by inhibiting phagosome-lysosome fusion and cellular trafficking. May act by disrupting the function of the mammalian HOOK3 protein, a protein involved in the cellular traffic. Interacts with the mammalian NIPSNAP3A and HOOK3 proteins in infected cells. Translocated into the cytosol of macrophages via the Salmonella pathogenicity island 2 (SPI-2) type III secretion system that functions intracellularly to translocate proteins across the phagosomal membrane. Cytoplasmic in infected macrophages. PubMed:12174087 and PubMed:12193612 report that SpiC is not translocated into the infected cell, and is localized in the bacterial cytoplasm. They show it is required for secretion of SseB and SseC virulence proteins into infected cells.