Staphylococci: Colonizers and Pathogens of Human Skin

Rosanna Coates; Josephine Moran; Malcolm J Horsburgh

Disclosures

Future Microbiol. 2014;9(1):75-91. 

In This Article

Secreted Proteases

The induced expression of secreted proteases forms a key defense from AMPs in staphylococci. SepA metalloprotease increases S. epidermidis persistence by degradation of dermcidin.[72]S. epidermidis also upregulates agr, sarA and saeRS in response to the peptide dermcidin,[43] which corroborates findings that sepA is under the control of these global regulatory systems.[72] S. aureus metalloprotease aureolysin disables the human cathelicidin LL-37, which aids skin persistence and contributes to disease by limiting phagocytosis due to complement inhibition and increasing intracellular persistence.[73–75]

S. aureus is the etiological agent of protease-linked disease of the epidermis, such as staphylococcal scalded-skin syndrome. Epidermolytic toxins (ET) are a group of serine proteases that degrade the epidermal cadherin desmoglein-1 in the stratum granulosum;[76] desmoglein-3 compensates for breakdown of desmoglein-1 in other skin layers. Another serine protease, glutamylendopeptidase SspA (V8), shares both cleavage site and sequence similarity with ET and hydrolyzes desmoglein-1.[77] The application of SspA leads to a reduction in corneocyte abundance on the skin in a mouse model[78] resulting in speculation that ET and V8 proteases undermine the barrier function of the skin, allowing invasion.[79] In this way, they might act in concert with β-hemolysin promoting colonization, and this exoprotein is cytotoxic to primary keratinocytes.[80]

Cysteine proteases also impact upon staphylococcal skin persistence. Staphopain A and B in S. aureus and Ecp in S. epidermidis catalyze the breakdown of both elastin and collagen, which is an abundant polymer on the skin.[81,82]

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