Keratin 23, a novel DPC4/Smad4 target gene which binds 14-3-3ε.

Background: Inactivating mutations of SMAD4 are frequent in metastatic colorectal carcinomas. In previous analyses, we were able to show that restoration of Smad4 expression in Smad4-deficient SW480 human colon carcinoma cells was adequate to suppress tumorigenicity and invasive potential, whereas in vitro cell growth was not affected. Using this cellular model system, we searched for new Smad4 targets comparing nuclear subproteomes derived from Smad4 re-expressing and Smad4 negative SW480 cells.

Identification of protein disulfide isomerase as a cardiomyocyte survival factor in ischemic cardiomyopathy.

Objectives: The aim of the study was to analyze the molecular mechanisms activated during postinfarction remodeling in human hearts.

Background: The molecular mechanisms of initial response to ischemic insult in the heart and the pathways involved in compensation and remodeling are still largely unknown.

Methods: Up-regulation or down-regulation of gene expression in the human viable peri-infarct (vs.

Differential regulation of cell volume and shape in confluent rat hepatocytes under hypertonic stress.

In confluent primary cultures of rat hepatocytes,hypertonic stress leads to cell shrinkage and activates non-selective cation channels as the main mechanism of regulatory cell volume increase. The process is found to employ the exocytotic insertion of channels into the plasma membrane and (in addition to PKC) PLC, tyrosine kinases and G proteins, but not PI 3-kinase are part of the signalling network. Furthermore, hypertonic stress leads to the formation of stress fibres and significantly alters the activity of RhoA, Rac and Cdc42.

p190-RhoGAP as an integral component of the Tiam1/Rac1-induced downregulation of Rho.

The Rho family of small GTPases plays a central role in intracellular signal transduction, particularly in reorganization of the actin cytoskeleton. Rho activity induces cell contractility, whereas Rac promotes cellular protrusion, which counteracts Rho signaling. In this regard, the reciprocal balance between these GTPases determines cell morphology and migratory behavior.

Purification and biochemical properties of Rac1, 2, 3 and the splice variant Rac1b.

Rac proteins (Rac1, 1b, 2, 3) belong to the GTP-binding proteins (or GTPases) of the Ras superfamily and thus act as molecular switches cycling between an active GTP-bound and an inactive GDP-bound form through nucleotide exchange and hydrolysis. Like most other GTPases, these proteins adopt different conformations depending on the bound nucleotide, the main differences lying in the conformation of two short and flexible loop structures designated as the switch I and switch II region. The three distinct mammalian Rac isoforms, Rac1, 2 and 3, share a very high sequence identity (up to 90%), with Rac1b being an alternative splice variant of Rac1 with a 19 amino acid insertion in vicinity to the switch II region.

aRNA-longSAGE: a new approach to generate SAGE libraries from microdissected cells.

Large-scale gene expression analyses of microdissected primary tissue are still difficult because generally only a limited amount of mRNA can be obtained from microdissected cells. The introduction of the T7-based RNA amplification technique was an important step to reduce the amount of RNA needed for such analyses. This amplification technique produces amplified antisense RNA (aRNA), which so far has precluded its direct use for serial analysis of gene expression (SAGE) library production.

The RacGEF Tiam1 inhibits migration and invasion of metastatic melanoma via a novel adhesive mechanism.

Rho-like GTPases such as RhoA, Rac1 and Cdc42 are key regulators of actin-dependent cell functions including cell morphology, adhesion and migration. Tiam1 (T lymphoma invasion and metastasis 1), a guanine nucleotide exchange factor that activates Rac, is an important regulator of cell shape and invasiveness in epithelial cells and fibroblasts. Overexpression of Tiam1 in metastatic melanoma cells converted the constitutive mesenchymal phenotype into an epithelial-like phenotype.

Alternative splicing of Rac1 generates Rac1b, a self-activating GTPase.

Rac1b was recently identified in malignant colorectal tumors as an alternative splice variant of Rac1 containing a 19-amino acid insertion next to the switch II region. The structures of Rac1b in the GDP- and the GppNHp-bound forms, determined at a resolution of 1.75 A, reveal that the insertion induces an open switch I conformation and a highly mobile switch II.

The RhoGAP activity of OPHN1, a new F-actin-binding protein, is negatively controlled by its amino-terminal domain.

Recent human genetic approaches showed that mutations in three genes encoding OPHN1, PAK3, and alphaPIX cause nonspecific X-linked mental retardation. These three proteins act to modulate Rho GTPase signaling pathways and may participate in neuronal morphogenesis by regulating the actin cytoskeleton. Here we showed that the Oligophrenin-1 gene is expressed in the developing spinal cord and later in brain areas that are characterized by high synaptic plasticity.

The new sulindac derivative IND 12 reverses Ras-induced cell transformation.

The nonsteroidal anti-inflammatory drug Sulindac has chemopreventive and antitumorigenic properties. Its metabolites induce apoptosis and inhibit signaling pathways critical for malignant transformation, including the Ras pathway. Here we show that the new Sulindac derivative IND 12 reverses the phenotype of Ras-transformed MDCK-f3 cells and restores an untransformed epithelioid morphology characterized by growth in monolayers with regular cell-cell adhesions.

Rap-specific GTPase activating protein follows an alternative mechanism.

Rap1 is a small GTPase that is involved in signal transduction cascades. It is highly homologous to Ras but it is down-regulated by its own set of GTPase activating proteins (GAPs). To investigate the mechanism of the GTP-hydrolysis reaction catalyzed by Rap1GAP, a catalytically active fragment was expressed in Escherichia coli and characterized by kinetic and mutagenesis studies.