RNase 7 contributes to the cutaneous defense against Enterococcus faecium.
BACKGROUND
Human skin is able to mount a fast response against invading microorganisms by the release of antimicrobial proteins such as the ribonuclease RNase 7. Because RNase 7 exhibits high activity against Enterococcus faecium the aim of this study was to further explore the role of RNase 7 in the cutaneous innate defense system against E. faecium.


RESULTS
Absolute quantification using real-time PCR and ELISA revealed that primary keratinocytes expressed high levels of RNase 7. Immunohistochemistry showed RNase 7 expression in all epidermal layers of the skin with an intensification in the upper more differentiated layers. Furthermore, RNase 7 was secreted by keratinocytes in vitro and in vivo in a site-dependent way. RNase 7 was still active against E. faecium at low pH (5.5) or high NaCl (150 mM) concentration and the bactericidal activity of RNase 7 against E. faecium required no ribonuclease activity as shown by recombinant RNase 7 lacking enzymatic activity. To further explore the role of RNase 7 in cutaneous defense against E. faecium, we investigated whether RNase 7 contributes to the E. faecium killing activity of skin extracts derived from stratum corneum. Treatment of the skin extract with an RNase 7 specific antibody, which neutralizes the antimicrobial activity of RNase 7, diminished its E. faecium killing activity.


CONCLUSIONS
Our data indicate that RNase 7 contributes to the E. faecium-killing activity of skin extracts and suggest an important role for RNase 7 in the protection of human skin against E. faecium colonization.
Köten
Bente
B
Department of Dermatology, University Hospital Schleswig-Holstein, Campus Kiel, Kiel, Germany.
Simanski
Maren
M
Gläser
Regine
R
Podschun
Rainer
R
Schröder
Jens-Michael
JM
Harder
Jürgen
J
D016984:Enterococcus faecium / Q000472:pathogenicity*; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D007150:Immunohistochemistry; D016133:Polymerase Chain Reaction; D012260:Ribonucleases / Q000378:metabolism*; D012867:Skin / Q000201:enzymology / Q000382:microbiology*
D012260:Ribonucleases; C470000:Ribonuclease 7