Klk5 is a key regulator of epidermal proteolysis.

<p><i>In situ</i> zymography using fluorescence-quenched casein (<b>A)</b> or elastin (<b>B</b>). Skin tissue sections were prepared from wt, <i>Spink5</i>^<i>-/-</i>, <i>Klk5</i>^<i>-/-</i>, and <i>Spink5</i>^<i>-/-</i><i>Klk5</i>^<i>-/-</i> mice. Ablation of <i>Klk5</i> expression highly reduced both caseinolytic and elastinolytic activities in the <i>stratum corneum</i> of <i>Spink5</i>^<i>-/-</i><i>Klk5</i>^<i>-/-</i> as compared to <i>Spink5</i>^<i>-/-</i>, respectively. Fluorescence intensity data was transformed into a color gradient (as shown) using ImageJ software. Dashed white lines represent the dermal-epidermal junction; <u>The asterisk (*) indicates the epidermis, scale bar: 25μm</u> (<b>C</b>) Changes in proteolytic activity using colorimetric substrates that target different proteases. Activity in wt, <i>Spink5</i>^<i>-/-</i> and <i>Spink5</i>^<i>-/-</i><i>Klk5</i>^<i>-/-</i> was detected by measuring absorbance at 405 nm after overnight incubation with substrates for either KLK7 or KLK14. Data are shown as the mean ± SEM of duplicates for four mice per genotype; (<b>D</b>) Analysis of mRNA expression in skin by RT-qPCR of Klk7 and Klk14. Results show high expression of both Klks in <i>Spink5</i>^<i>-/-</i>. In <i>Spink5</i>^<i>-/-</i><i>Klk5</i>^<i>-/-</i> skin, expression of Klk14 is equal to wt while Klk7 remained slightly higher. Data are shown as the mean ± s.e.m. of triplicate amplification for at least three mice per genotype. Results are normalized to wt mean (set as 1.0).