Ultrastructural distribution of the S100A1 Ca2+-binding protein in the human heart

Impaired calcium homeostasis and altered expression of Ca2+-binding proteins are associated with cardiomyopathies, myocardial hypertrophy, infarction or ischemia. S100A1 protein with its modulatory effect on different target proteins has been proposed as one of potential candidates which could participate in these pathological processes. The exact localization of S100A1 in human heart cells on the ultrastructural level accompanied with biochemical determination of its target proteins may help clarify the role of S100A1 in heart muscle. In the present study the distribution of the S100A1 protein using postembedding (Lowicryl K4M) immunocytochemical method in human heart muscle has been determined quantitatively, relating number of antigen sites to the unit area of a respective structural component. S100A1 antigen sites have been detected in elements of sarcoplasmic reticulum (SR), in myofibrils at all levels of sarcomere and in mitochondria, the density of immunolabeling at Z-lines being about 3 times and at SR more than 5 times higher than immunolabeling of remaining structural components. The presence of the S100A1 in SR and myofibrils may be related to the known target proteins for S100A1 at these sites

Discovery of a Potent and Selective DDR1 Receptor Tyrosine Kinase Inhibitor

The DDR1 receptor tyrosine kinase is activated by matrix collagens and has been implicated in numerous cellular functions such as proliferation, differentiation, adhesion, migration, and invasion. Here we report the discovery of a potent and selective DDR1 inhibitor, DDR1-IN-1, and present the 2.2 Å DDR1 co-crystal structure. DDR1-IN-1 binds to DDR1 in the ‘DFG-out’ conformation and inhibits DDR1 autophosphorylation in cells at submicromolar concentrations with good selectivity as assessed against a panel of 451 kinases measured using the KinomeScan technology. We identified a mutation in the hinge region of DDR1, G707A, that confers >20-fold resistance to the ability of DDR1-IN-1 to inhibit DDR1 autophosphorylation and can be used to establish what pharmacology is DDR1-dependent. A combinatorial screen of DDR1-IN-1 with a library of annotated kinase inhibitors revealed that inhibitors of PI3K and mTOR such as GSK2126458 potentiate the antiproliferative activity of DDR1-IN-1 in colorectal cancer cell lines. DDR1-IN-1 provides a useful pharmacological probe for DDR1-dependent signal transduction

S100A1: A Multifaceted Therapeutic Target in Cardiovascular Disease

Cardiovascular disease is the leading cause of death worldwide, showing a dramatically growing prevalence. It is still associated with a poor clinical prognosis, indicating insufficient long-term treatment success of currently available therapeutic strategies. Investigations of the pathomechanisms underlying cardiovascular disorders uncovered the Ca2+ binding protein S100A1 as a critical regulator of both cardiac performance and vascular biology. In cardiomyocytes, S100A1 was found to interact with both the sarcoplasmic reticulum ATPase (SERCA2a) and the ryanodine receptor 2 (RyR2), resulting in substantially improved Ca2+ handling and contractile performance. Additionally, S100A1 has been described to target the cardiac sarcomere and mitochondria, leading to reduced pre-contractile passive tension as well as enhanced oxidative energy generation. In endothelial cells, molecular analyses revealed a stimulatory effect of S100A1 on endothelial NO production by increasing endothelial nitric oxide synthase activity. Emphasizing the pathophysiological relevance of S100A1, myocardial infarction in S100A1 knockout mice resulted in accelerated transition towards heart failure and excessive mortality in comparison with wild-type controls. Mice lacking S100A1 furthermore displayed significantly elevated blood pressure values with abrogated responsiveness to bradykinin. On the other hand, numerous studies in small and large animal heart failure models showed that S100A1 overexpression results in reversed maladaptive myocardial remodeling, long-term rescue of contractile performance, and superior survival in response to myocardial infarction, indicating the potential of S100A1-based therapeutic interventions. In summary, elaborate basic and translational research established S100A1 as a multifaceted therapeutic target in cardiovascular disease, providing a promising novel therapeutic strategy to future cardiologists

Notch and Senescence.

Cellular senescence, previously thought of as an autonomous tumour suppressor mechanism, is emerging as a phenotype and effector present throughout the life of an organism from embryogenesis to senile decline. Senescent cells have powerful non-autonomous effects upon multiple players within their microenvironment mainly through their secretory phenotype. How senescent cells co-ordinate numerous, sometimes functionally contrasting outputs through their secretome had previously been unclear. The Notch pathway, originally identified for its involvement in Drosophila wing development, has more recently been found to underpin diverse effects in human cancer. Here we discuss recent findings that suggest that Notch is intimately involved in the development of senescence and how it acts to co-ordinate the composition and functional effects of the senescence secretome. We also highlight the complex physical and functional interplay between Notch and p53, critical to both senescence and cancer. Understanding the interplay between Notch, p53 and senescence could allow us develop the therapeutics of the future for cancer and ageing

Joining S100 proteins and migration:for better or for worse, in sickness and in health

The vast diversity of S100 proteins has demonstrated a multitude of biological correlations with cell growth, cell differentiation and cell survival in numerous physiological and pathological conditions in all cells of the body. This review summarises some of the reported regulatory functions of S100 proteins (namely S100A1, S100A2, S100A4, S100A6, S100A7, S100A8/S100A9, S100A10, S100A11, S100A12, S100B and S100P) on cellular migration and invasion, established in both culture and animal model systems and the possible mechanisms that have been proposed to be responsible. These mechanisms involve intracellular events and components of the cytoskeletal organisation (actin/myosin filaments, intermediate filaments and microtubules) as well as extracellular signalling at different cell surface receptors (RAGE and integrins). Finally, we shall attempt to demonstrate how aberrant expression of the S100 proteins may lead to pathological events and human disorders and furthermore provide a rationale to possibly explain why the expression of some of the S100 proteins (mainly S100A4 and S100P) has led to conflicting results on motility, depending on the cells used. © 2013 Springer Basel

Structure, assembly, and dynamics of actin filaments in situ and in vitro

Actin, though highly conserved, exhibits a myriad of diverse functions, most of which ultimately depend on its intrinsic ability to rapidly assemble and disassemble filamentous structures. Many organisms synthesize multiple actin isoforms even within the same cell. Tissue-specific expression patterns and tight developmental regulation as well as a high conservation across species emphasize the functional importance of isoforms. The detailed knowledge of the structure, assembly, and dynamic behavior of actin provides important pieces in solving the puzzle of how the different isoforms can be so versatile despite their extremely high sequence identity

Small GTPase RhoE/Rnd3 is a critical regulator of Notch1 signaling.

Aberrations of Notch signaling have been implicated in a variety of human cancers. Oncogenic mutations in NOTCH1 are common in human T-cell leukemia and lymphomas. However, loss-of-function somatic mutations in NOTCH1 arising in solid tumors imply a tumor suppressor function, which highlights the need to understand Notch signaling more completely. Here, we describe the small GTPase RhoE/Rnd3 as a downstream mediator of Notch signaling in squamous cell carcinomas (SCC) that arise in skin epithelia. RhoE is a transcriptional target of activated Notch1, which is attenuated broadly in SCC cells. RhoE depletion suppresses Notch1-mediated signaling in vitro, rendering primary keratinocytes resistant to Notch1-mediated differentiation and thereby favoring a proliferative cell fate. Mechanistic investigations indicated that RhoE controls a key step in Notch1 signaling by mediating nuclear translocation of the activated portion of Notch1 (N1IC) through interaction with importins. Our results define RhoE as a Notch1 target that is essential for recruitment of N1IC to the promoters of Notch1 target genes, establishing a regulatory feedback loop in Notch1 signaling. This molecular circuitry may inform distinct cell fate decisions to Notch1 in epithelial tissues, where carcinomas such as SCC arise. Cancer Res; 74(7); 2082-93. ©2014 AACR