perforin2

Perforin-2, also known as macrophage-expressed gene 1 (MPEG1), is a pore-forming protein of the membrane attack complex/perforin (MACPF) superfamily. It is expressed predominantly by macrophages and other phagocytic cells and serves as an important component of the innate immune defense against bacteria.

MPEG1 is stored in endolysosomal compartments and associated membranes within phagocytes. Following uptake of bacteria, phagosomes fuse with lysosomes, and Perforin-2 is mobilized to the phagosomal membrane where it can form pores in bacterial envelopes. This pore formation disrupts bacterial membranes and promotes bacterial killing, often acting in concert with other antimicrobial effectors.

Expression and activity of MPEG1 are upregulated by inflammatory signals, including interferon-gamma (IFN-γ) and toll-like receptor (TLR) signaling. As a MACPF family member, Perforin-2 shares the characteristic ability to assemble transmembrane pores that compromise target membranes, contributing to intracellular bacterial clearance.

In animal models, loss of MPEG1 function can lead to reduced control of certain intracellular bacterial pathogens, indicating a contributory role in host defense. In humans, MPEG1 is expressed in macrophages and dendritic cells, but the full clinical significance of Perforin-2 remains under investigation.

Perforin-2 is one of several MACPF family perforins, distinct from perforin-1 used by cytotoxic lymphocytes. It is commonly referred to by its alias MPEG1 and is considered a component of the innate cellular arsenal against intracellular bacteria.