Calcium-binding protein S100A7 and epidermal-type fatty acid-binding protein are associated in the cytosol of human keratinocytes

Abstract

Expression of epidermal-type fatty acid-binding protein (E-FABP) and S100A7 has previously been shown to be elevated in psoriatic skin, a disease characterized by abnormal keratinocyte differentiation. However, no causal relationship between the up-regulation of these proteins and the disease has been shown. E-FABP is thought to be involved in cytosolic fatty acid (FA) transport, whereas the role of S100A7 is still unknown. In this report, we show by overlay assays that E-FABP, immobilized on nitrocellulose, is able to capture S100A7 from cytosolic psoriatic protein extracts and vice versa, suggesting the formation of a complex between the two proteins. Using purified E-FABP and S100A7, the complex can be reconstituted only in presence of EDTA. Moreover, we show that increased EDTA concentrations in psoriatic cytosolic protein extracts enhance complex formation. Partial complex disruption was obtained by the addition of physiological concentrations of Zn2+ (0.1 mM), whereas Ca2+ at 5 mM and Mg2+ at 30 mM had no effect. On the other hand, high Ca2+ concentrations (30 mM) resulted in partial complex disruption. Oleic acid-binding properties were observed for free E-FABP and the complex E-FABP-S100A7, but not for free S100A7. By using confocal microscopy we show that S100A7 and E-FABP are co-localized in the cytoplasm of differentiating keratinocytes from lesional psoriatic skin. These data indicate that formation of the E-FABP-S100A7 complex and its FA-binding function might be regulated at least by bivalent cations.

S100 Proteins in the Epidermis

“…Siegenthaler and colleagues confirmed that E-FABP level is elevated in psoriasis and showed that immunoprecipitation of psoriatic scale extracts with anti-E-FABP results in co-immunoprecipitation of S100A7 (Hagens et al, 1999b). Additional studies showed that nitrocellulose-immobilized E-FABP can bind S100A7 (Hagens et al, 1999a). A recent study that examines S100A7 and E-FABP distribution and interaction in cultured normal human keratinocytes (Ruse et al, 2003) confirms and extends the observations of Siegenthaler et al (Hagens et al, 1999a, b).…”

“…in oleic acid transport and metabolism (Hagens et al, 1999a). Oleic acid may have a role in inflammation, as topical application modulates epidermal Langerhans cells density (Touitou et al, 2002).…”

Blood Coagulation and Living Tissue Sterilization by Floating-Electrode Dielectric Barrier Discharge in Air

“…provided by hydrogen ions generated in air plasma through a sequence of ion-molecular processes [24] (here R represents calcium-binding protein complexes, like S100A7, for example [25]). Though the reaction is reversible, we will neglect contribution of reverse reaction (k −Ca ) due to abundance of H + ions generated by e-plasma in the following mechanism (here X (H 2 O) signifies ion X dissolved in water):…”

The cytoplasmic fatty-acid-binding proteins: thirty years and counting

“…It is not clear how activation of LCFA binding occurs, but recent reports indicate that such aspects may be important. E-FABP C can bind the protein S100A7 (function unknown) to form a complex that can bind fatty acid in a manner that is modulated by divalent cations [189]. Although heme is normally kept at very low concentrations, ferriheme and ferroheme can compete LCFAs from rat L-FABP C isosterically with the K i for ferroheme threefold smaller than the Fe III state [190].…”