Meprin α and meprin β: Procollagen proteinases in health and disease

•Meprin metalloproteases are important enzymes for fibrillar collagen deposition.•Meprin α and meprin β both cleave off C- and N-propeptides of collagens I and III.•Maturation of procollagen I by meprins results in spontaneous fibrillogenesis.•Increased expression of meprins is associated with fibrotic conditions in the skin and the lung.•Meprin β is regulated by AP-1 transcription factor complex.

Metalloproteases meprin α and meprin β were recently discovered as procollagen proteinases, capable of cleaving off the globular C- and N-terminal prodomains of fibrillar collagen type I and type III. This proteolytic process is indeed sufficient to induce collagen fibril assembly as visualized by transmission electron microscopy. The biological relevance was demonstrated with the help of meprin α and meprin β knock-out mice, which exhibit decreased collagen deposition in skin resulting in impaired tensile strength. On the other hand, overexpression of meprin metalloproteases was found under fibrotic conditions in the skin (keloids) and the lung (pulmonary hypertension). Thus, regulation of meprin activity by specific inhibition to reduce collagen maturation might be a suitable approach for the treatment of certain pathological conditions.