hlgABC

hlgABC is a Staphylococcus aureus gene cluster that encodes the gamma-hemolysin leukocidin subunits A, B, and C. The cluster comprises three adjacent genes, hlgA, hlgB, and hlgC, and it gives rise to two related bicomponent toxins, HlgAB and HlgCB. In these toxins, HlgB serves as the common F subunit, pairing with HlgA to form HlgAB and with HlgC to form HlgCB.

Function and role in virulence

The gamma-hemolysin toxins are secreted pore-forming factors that lyse a range of host cells, notably neutrophils and other leukocytes, as well as some erythrocytes. By disrupting immune cell viability and function, HlgAB and HlgCB contribute to the cytotoxic profile of S. aureus and aid in immune evasion and tissue damage during infection. The toxins act by assembling on the target cell membrane and forming pores that disrupt cellular integrity.

Regulation and expression

hlgABC expression is governed by global regulatory networks in S. aureus, including the agr quorum-sensing system and saeRS two-component system. Expression tends to be influenced by growth phase and environmental conditions, reflecting the organism’s need to coordinate virulence factor production with its ecological niche and state of infection.

Structure and secretion

The hlgABC-encoded proteins are secreted by Staphylococcus aureus via the Sec pathway. After secretion, the HlgA/HlgB and HlgC/HlgB subcomplexes assemble on the surface of susceptible cells to form functional pores, leading to cell lysis.

Clinical relevance

The hlgABC locus is found in many S. aureus clinical isolates and is associated with leukotoxic activity. It is a focus of study for understanding virulence and for exploring potential therapeutic or vaccine targets against staphylococcal infections.

See also

Panton-Valentine leukocidin, LukED, leukocidins in Staphylococcus aureus.