Proteases play a pivotal role in epidermal differentiation and desquamation. Separation of a total protein extract from @entity1 reconstructed epidermis by two-dimensional gel electrophoresis and subsequent peptide analysis of a specific protein spot identified a new protein exhibiting similarities with the retroviral aspartic protease family. Cloning of the corresponding full-length cDNA revealed an open reading frame encoding for a new protease of 343 @entity1522 , containing a putative aspartic protease catalytic domain. We named this protein @entity19743 ( @entity19743 ). RT-PCR and northern blot analysis of various @entity1 tissues revealed that @entity19743 was specifically expressed within the epidermis. Immunohistochemical analysis showed a particularly intense expression restricted to the granular layers, whereas in diseased skin, its expression was changed. Western blot analysis, using a monoclonal antibody, revealed the expression of two forms of the enzyme: a 28 kDa putative proform and the active 14 kDa form. Recombinant truncated @entity19743 (SASP28) was generated from a prokaryotic expression system in @entity526 as a fusion protein with GST. SASP28 degraded insulin and to a lesser extent casein with a pH optimum of 5. As seen for retroviral proteases, an auto-activation processing was evidenced, generating a 14 kDa protein (SASP14). Site-directed mutagenesis inhibited auto-activation of the enzyme. @entity5190 , a potent @entity645 protease inhibitor used in AIDS therapy, had a significant inhibitory effect on rSASPase auto-activation, which could explain its side effects on skin.

Identification and characterization of a novel retroviral-like aspartic protease specifically expressed in XXXX epidermis.

@entity1 :: ('9606', 'Species') :: ['human'] @entity1522 :: ('CHEBI:33709', 'Chemical') :: ['amino acids'] @entity5190 :: ('MESH:D019469', 'Chemical') :: ['Indinavir'] @entity645 :: ('57667', 'Species') :: ['HIV'] @entity19743 :: ('151516', 'Gene') :: ['Skin ASpartic Protease', 'SASPase'] @entity526 :: ('562', 'Species') :: ['Escherichia coli']
@entity1 :: (9606,Species) :: ['human']
