Small hydrophobic (SH) proteins of Pneumoviridae and Paramyxoviridae : small but mighty

Abstract

ABSTRACT Small hydrophobic (SH) proteins are a class of viral accessory proteins expressed by many members of the negative-stranded RNA viral families Paramyxoviridae and Pneumoviridae . Identified SH proteins are type I or II transmembrane (TM) proteins with a single-pass TM domain. Little is known about the functions of SH proteins; however, several possess viroporin activity, enhancing membrane permeability of infected cells or those expressing SH protein. Moreover, several SH proteins inhibit apoptosis and immune signaling pathways within infected cells, including TNF and interferon signaling, or activate inflammasomes. SH proteins are generally nonessential for viral replication in vitro , but loss of SH is often associated with reduced replication in vivo , suggesting a role in enhancing viral replication or evading host immunity. Analogous proteins are expressed by a variety of pathogens of public health importance; thus, understanding the functional importance and mechanisms of SH proteins provides insight into the pathogenesis and replication of negative-sense RNA viruses.