Deletion of cysteine cathepsins B or L yields differential impacts on murine skin proteome and degradome

10.12.2012

Tholen S, Biniossek ML, Gansz M, Gomez-Auli A, Werner F, Noel A, Kizhakkedathu JN, Boerries M, Busch H, Reinheckel T, Schilling O.

Mol Cell Proteomics. 2013 Mar;12(3):611-25

Mol Cell Proteomics.        online article

Numerous studies highlight that concerted proteolysis is essential for skin morphology and function. The cysteine protease cathepsin L (Ctsl) has been implicated in epidermal proliferation and desquamation as well as in hair cycle
regulation. In stark contrast, mice deficient for cathepsin B (Ctsb) do not display an overt skin phenotype. To understand the systematic consequences of deleting Ctsb or Ctsl, we determined protein abundances of > 1300 proteins and
proteolytic cleavage events in skin samples of wild-type, Ctsb-/- and Ctsl-/- mice by mass spectrometry based proteomics. Both protease deficiencies revealed distinct quantitative changes in proteome composition. Ctsl-/- skin revealed
increased levels of the cysteine protease inhibitors cystatin B and cystatin M/E, increased cathepsin D and accumulation of the extracellular glycoprotein periostin. Immunohistochemistry located periostin predominantly in hypodermal
connective tissue of Ctsl-/- skin. Proteomic identification of proteolytic cleavage sites within skin proteins revealed numerous processing sites that are underrepresented in Ctsl-/- or Ctsb-/- samples. Notably, few of the affected
cleavage sites shared the canonical Ctsl or Ctsb specificity, providing further evidence for a complex proteolytic network in the skin. Novel processing sites in proteins such as dermokine and Notch-1 were detected. Simultaneous analysis of acetylated protein N-termini showed prototypical mammalian N-alpha acetylation. These results illustrate an influence of both Ctsb and Ctsl on the murine skin proteome and degradome with the phenotypic consequences of the absence of either protease differing considerably.