ABSTRACT
Human recombinant, baculovirus-expressed p53 protein focuses on 2D gels in multiple spots in the narrow pI range. Re-electrophoresis of the individual spots resulted in the appearance of multiple spots. The strings of spots were neither species specific, nor characteristic for baculovirus-expressed p53. Moreover, mutant p53 did not deviate from wild-type p53, indicating that this is an inherent property of p53. Okadaic acid treatment of insect cells, phosphate substitution reaction of purified p53, and individual analysis of all spots by mass spectrometry revealed that only a fraction of the recombinant p53 is phosphorylated. This finding excluded that the individual p53 spots in 2D gels reflect charge isomers generated by phosphorylation, but rather suggest that they are due to conformational flexibility of urea-denatured monomeric p53 molecules or deamidation of asparagine and glutamine residues. The latter possibility was confirmed by NanoLC-ESI MS/MS analysis. Our data provide a putative hint for a novel regulatory level for function and stability of p53, particularly the long-lived mutant p53 overexpressed in diverse tumor types.
Subject(s)
Isoelectric Focusing/methods , Recombinant Proteins/chemistry , Tumor Suppressor Protein p53/chemistry , Amino Acid Sequence , Animals , Baculoviridae/genetics , Cell Line , Electrophoresis, Gel, Two-Dimensional , Humans , Mice , Molecular Sequence Data , Moths , Phosphorylation , Recombinant Proteins/genetics , Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization , Tumor Suppressor Protein p53/geneticsABSTRACT
BACKGROUND: The decrease in firmness is a hallmark of skin aging. Accelerated by chronic sun exposure, fundamental changes occur within the dermal extracellular matrix over the years, mainly impairing the collagenous network. AIMS: Based on the qualitative and quantitative assessment of skin firmness, in vitro and in vivo studies were carried out to elucidate the effects of topical folic acid and creatine to counteract this age-dependent reduction in the amount of collagen. PATIENTS/METHODS: Topical application of a commercially available formulation containing folic acid and creatine was performed to study effects on skin firmness in vivo using cutometric analysis. Imaging and quantification of collagen density were carried out using multiphoton laser scanning microscopy (MPLSM). To investigate the effects of these compounds on collagen gene expression, procollagen synthesis, and collagen fibril organization, complementary in vitro studies on cultured fibroblast-populated collagen gels were carried out. RESULTS: The underlying structural changes in the collagen network of young and aged sun-exposed facial skin in vivo were visualized by MPLSM. Topical application of a folic acid- and creatine-containing formulation significantly improved firmness of mature skin in vivo. Treatment of fibroblast-populated dermal equivalents with folic acid and creatine increased collagen gene expression and procollagen levels and improved collagen fiber density, suggesting that the in vivo effects are based on the overall improvement of the collagen metabolism. CONCLUSIONS: Employing MPLSM, dermal changes occurring in photo-aged human skin were visualized in an unprecedented manner and correlated to a loss of firmness. Treatment of aged skin with a topical formulation containing folic acid and creatine counteracted this age-dependent decline by exerting sustained effects on collagen metabolism. Our results support previous findings on the efficacy of these actives.
Subject(s)
Collagen/drug effects , Creatinine/pharmacology , Folic Acid/pharmacology , Skin Aging/drug effects , Skin/drug effects , Vitamin B Complex/pharmacology , Administration, Topical , Adult , Aged , Cells, Cultured , Collagen/genetics , Collagen/metabolism , Elasticity/drug effects , Female , Fibroblasts/drug effects , Fibroblasts/metabolism , Gene Expression/drug effects , Humans , Microscopy/methods , Middle Aged , Procollagen/metabolism , RNA, Messenger/metabolism , Skin/ultrastructure , Sunlight/adverse effects , Young AdultABSTRACT
Psoriasin (S100A7) was identifi;ed as a gene highly expressed in psoriatic keratinocytes and highly and more frequently expressed in ductal carcinoma in situ (DCIS) than in invasive breast carcinomas (IBC), suggesting a potential role in tumor progression. Psoriasin expression is associated with poor prognostic factors in both DCIS and IBC. Several putative functions have been proposed for psoriasin in various disease types, but none of these can fully explain its involvement in breast tumor progression. Here, we show that down-regulation of endogenous psoriasin expression via stable short hairpin RNAs in a human IBC cell line (MDA-MB-468) increases cell migration and invasion without influencing cell proliferation and survival in vitro but inhibits tumor growth in vivo. These seemingly paradoxical results are potentially explained by the dramatic up-regulation and down-regulation of matrix metalloproteinase-13 and vascular endothelial growth factor (VEGF), respectively, observed in cells with decreased psoriasin levels compared with controls. Correlating with this, high psoriasin expression in human IBC is associated with increased angiogenesis and worse clinical outcome, and psoriasin mRNA levels are coordinately regulated with VEGF and other genes related to hypoxia and mitochondrial reactive oxygen species (ROS). Based on these results, we propose that psoriasin may play a role in breast tumor progression by promoting angiogenesis and enhancing the selection for cells that overcome its anti-invasive function. This hypothesis may explain why psoriasin expression is highest in high-grade and/or estrogen receptor-negative tumors, as these are associated with increased hypoxia and ROS, a setting in which the angiogenic effects of psoriasin are most important.
