Steroid hormones influence a plethora of cellular functions, depending on the nature of the target cell and the constellation of signals impinging on the cell at a given time. To achieve the necessary coordination with other signaling pathways in the complex intracellular space, steroid hormones likely use a variety of mechanisms. Until very recently, attention has mainly been focused on the transcriptional effects of steroid hormones. These responses are mediated by the intracellular hormone receptors, which participate in multiple interactions with DNA, other sequence-specific transcription factors, transcriptional coregulators, and the general transcriptional machinery (3). In the last few years, a great effort has been devoted to understanding the nature of the transcriptional coregulators and how they mediate the interaction of the hormone receptors with chromatin remodelling complexes and the transcriptional apparatus (18). Considerable progress has been achieved, leading to the recognition of covalent and conformational chromatin changes as key steps in transcriptional regulation by steroid hormone receptors and other transcription factors (5).In addition to their direct transcriptional effects, steroid hormones have been found to influence the activity of many other signaling pathways by so-called "nongenomic mechanisms" (25,34,38). These effects are mediated by interactions at the membrane or cytoplasmic level and offer a possibility for integration of the steroid hormone signals at the entry site of many other physiological signals acting via membrane receptors (39). Very often, these nongenomic effects have been attributed to poorly characterized receptors, whose relationship with the conventional nuclear receptors remains unclear (38). In the case of the ovarian hormones estrogens and progestins, cross talk with a number of other signaling pathways has been described, including cyclic AMP (1, 16), Ca-calmodulin (15), the G protein-coupled receptors (20), and the mitogen-activated protein (MAP) kinase pathway (25,26). In breast cancer cells, estrogens stimulate cell proliferation, and this effect can be blocked by inhibitors of the MAP kinase signaling pathway (30) or by intracellular calcium chelators (22). This pathway is activated by estrogens through an interaction of the classical estrogen receptor alpha (ER␣) with c-Src, which can be detected by coimmunoprecipitation (30). c-Src activity is enhanced 2 min after addition of 17␤-estradiol, reaches a peak after 5 min, and returns to basal levels after 15 to 30 min. Activation of c-Src can be inhibited by steroidal and nonsteroidal antiestrogens and is followed by transient activation of Ras, Raf, and Erk1/2 (7, 31). The participation of the classical ER␣ in activation of the mitogenic pathway was demonstrated in gene transfection studies in COS-7 cells (31). Activation of the cascade in these cells by estrogens was strictly dependent on transfection of ER␣, was inhibited by antiestrogens, and led to the formation of a complex of ER␣ and c-Src. Simi...

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Anticalins engineered for high affinity and specificity towards the central VFFAED epitope in Aβ peptides potently inhibit their aggregation, thus providing novel reagents to study the molecular pathology of Alzheimer's disease (AD) and alternative drug candidates compared with current biopharmaceutical treatments.

Several studies have shown the protective effects of dietary enrichment of various lipids in several late-onset animal models of Alzheimer Disease (AD); however, none of the studies has determined which structure within a lipid determines its detrimental or beneficial effects on AD. High-sensitivity enzyme-linked immunosorbent assay (ELISA) shows that saturated fatty acids (SFAs), upstream omega-3 FAs, and arachidonic acid (AA) resulted in significantly higher secretion of both A␤ 40 and 42 peptides compared with long chain downstream omega-3 and monounsaturated FAs (MUFA). Their distinct detrimental action is believed to be due to a structural template found in their fatty acyl chains that lack SFAs, upstream omega-3 FAs, and AA. Immunoblotting experiments and use of APP-C99-transfected COS-7 cells suggest that FAdriven altered production of A␤ is mediated through ␥-secretase cleavage of APP. An early-onset AD transgenic mouse model expressing the double-mutant form of human amyloid precursor protein (APP); Swedish (K670N/M671L) and Indiana (V717F), corroborated in vitro findings by showing lower levels of A␤ and amyloid plaques in the brain, when they were fed a low fat diet enriched in DHA. Our work contributes to the clarification of aspects of structure-activity relationships. Alzheimer Disease (AD)2 is a currently incurable progressive neurological disease that affects higher brain functions, ultimately leading to dementia and death (1). The molecular key event triggering the harmful cascade in AD is generally considered to be increased soluble oligomeric A␤, or more specifically A␤42 levels (2-4). Whereas A␤ generation depends on several factors, the prime event in A␤ generation is cleavage of APP-C99 by ␥-secretase. This is because it is the last essential step in A␤40 versus A␤42 generation, and it is also this cleavage for which most mechanistic information linking lipid homeostasis with A␤ production is available (5, 6).Several studies have shown the protective effects of various lipids on several parameters of AD; however, none of the studies has determined which structure within a lipid decides its detrimental or beneficial effects on A␤ production or the A␤40/42 ratio. Using an AD-cell culture model we identified the parameters, which may define whether a lipid or FA will affect A␤ production. A simple structure-activity relationship (SAR) study was performed in an attempt to examine the following factors: chain length, saturation, position of unsaturation (either at omega-3, -6, -7, or -9 carbon), and orientation (cis, trans) of double bonds as well as the effects of natural and synthetic/conjugated lipids. Based on our in vitro data, we designed a diet high in DHA but low in all deleterious fats and cholesterol, and showed for the first time in an early-onset robust mouse model of AD (which represents individuals who are at high risk of developing early-onset AD due to genetic mutations), that the protective structural template built-in the acyl chain of DHA indeed improves AD-type neuropathology...