Functional dissection of the granzyme family: cell death and inflammation

Cytotoxic lymphocytes rapidly respond and destroy both malignant cells and cells infected with intracellular pathogens. One mechanism, known as granule exocytosis, employs the secretory granules of these lymphocytes. These include the pore-forming protein perforin (pfp) and a family of serine proteases known as granzymes that cleave and activate effector molecules within the target cell. Over the past two decades, the study of granzymes has largely focused on the ability of these serine proteases to induce cell death. More recently, sophisticated mouse models of disease coupled with gene-targeted mice have allowed investigators to ask why granzyme subfamilies are encoded on different chromosomal loci and what broader role these enzymes might play in inflammation and immune response. Here, we provide a brief overview of the granzyme superfamily, their relationship to pfp, and their reported functions in apoptosis. This overview is followed by a comprehensive analysis of the less characterized and developing field regarding the non-apoptotic functions of granzymes.