Fig. 2

Conversion of constitutive proteasomes to immunoproteasomes. a Schematic representation for formation of 20S immunoproteasomes. To process antigens more efficiently, proteasomes replace some of its subunits to form immunoproteasomes. IFN-γ and TNF-α trigger transcriptional increases in IFN-γ that increase the expression of at least five immunoproteasome catalytic and activator subunits which cooperate to form 20S immunoproteasomes. New catalytic subunits (β1i, β2i, β5i) and activator subunits (PA28α/β) are incorporated into 20S constitutive proteasomes. b Genes that encode constitutive proteasome and immunoproteasome catalytic subunits, the catalytic activities and substrate specificities are shown. c Proteasome regulators that activate or inhibit proteasome-related activities are shown