The proteasome is a complex machinery in each cell which unfolds and breaks down proteins that are misfolded, damaged or no longer needed. The proteasome maturation protein (POMP) is essential for the assembly of this multiprotein complex and the incorporation of catalytic subunits. The proteasome is also involved in immune recognition and host defense and supports the immune response. When defective, it can lead to a dysregulated immune response and to autoimmunity and/or autoinflammatory diseases. Researchers have now discovered heterozygous truncating variants of the POMP gene in two patients with a unique combination of early-onset combined immunodeficiency, inflammatory neutrophilic dermatosis, and autoimmunity. Their functional investigations suggest a complex, dominant-negative mechanism in which de novo heterozygous frameshift variants of POMP escape nonsense-mediated mRNA decay and lead to a truncated protein that disturbs proteasome assembly.

The results of this study have been published in the American Journal of Human Genetics.