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D Radisky

Publications and source records attributed to D Radisky.

7 recordsLinked to original sources
PubMed2001

hVPS41 is expressed in multiple isoforms and can associate with vesicles through a RING-H2 finger motif.

Vps41p, the protein encoded by the yeast gene VPS41, has been shown to mediate formation of AP-3 transport vesicles from the Golgi apparatus and to facilitate the docking and fusion of lysosomal vesicles. Although both of these activities involve transient association with membrane structures, the mechanisms that mediate those interactions have not been determined. Orthologues of VPS41 have been identified in humans, Drosophila, tomato, and Arabidopsis; the degree of sequence similarity among these genes suggests a highly conserved function. Here we provide evidence that hVps41, the human homologue of Vps41p, is expressed in two isoforms that differ in that one contains a C-terminal RING-H2 sequence motif. Transient expression analysis suggests that this RING-H2 domain is responsible for membrane association. This observation was further supported by the cytosolic localization of site-specific mutants. A truncated construct containing only the hVps41 RING-H2 domain was found to associate with a class of intracellular vesicles that originated from the Golgi and showed partial coincidence with the delta subunit of the adaptor protein complex-3. Together with information from the homologous yeast system, these results suggest that hVps41 may also be involved in the formation and fusion of transport vesicles from the Golgi.

Amino Acid Sequence↗
PubMed2001

Epimorphin mediates mammary luminal morphogenesis through control of C/EBPbeta.

We have shown previously that epimorphin (EPM), a protein expressed on the surface of myoepithelial and fibroblast cells of the mammary gland, acts as a multifunctional morphogen of mammary epithelial cells. Here, we present the molecular mechanism by which EPM mediates luminal morphogenesis. Treatment of cells with EPM to induce lumen formation greatly increases the overall expression of transcription factor CCAAT/enhancer binding protein (C/EBP)beta and alters the relative expression of its two principal isoforms, LIP and LAP. These alterations were shown to be essential for the morphogenetic activities, since constitutive expression of LIP was sufficient to produce lumen formation, whereas constitutive expression of LAP blocked EPM-mediated luminal morphogenesis. Furthermore, in a transgenic mouse model in which EPM expression was expressed in an apolar fashion on the surface of mammary epithelial cells, we found increased expression of C/EBPbeta, increased relative expression of LIP to LAP, and enlarged ductal lumina. Together, our studies demonstrate a role for EPM in luminal morphogenesis through control of C/EBPbeta expression.

Animals↗
PubMed2001

Trichostatin A inhibits beta-casein expression in mammary epithelial cells.

Many aspects of cellular behavior are defined by the content of information provided by association of the extracellular matrix (ECM) and with cell membrane receptors. When cultured in the presence of laminin-containing ECM and prolactin (Prl), normal mammary epithelial cells express the milk protein beta-casein. We have previously found that the minimal ECM- and Prl-responsive enhancer element BCE-1 was only active when stably integrated into chromatin, and that trichostatin A (TSA), a reagent that leads to alterations in chromatin structure, was able to activate the integrated enhancer element. We now show that endogenous beta-casein gene, which is controlled by a genetic assembly that is highly similar to that of BCE-1 and which is also activated by incubation in ECM and Prl, is instead inhibited by TSA. We provide evidence that the differing response of beta-casein and BCE-1 to TSA is neither due to an unusual effect of TSA on mammary epithelial cells, nor to secondary consequences from the expression of a separate gene, nor to a particular property of the BCE-1 construct. As a component of this investigation, we also showed that ECM mediated rapid histone deacetylation in mammary epithelial cells. These results are discussed in combination with previous work showing that TSA mediates the differentiation of many types of cancer cells but inhibits differentiation of some nonmalignant cell types.

Acetylation↗
PubMed2001

Tumors are unique organs defined by abnormal signaling and context.

Many cancer investigations have focussed on the eradication of the cancer cell itself and in doing so, overlook the inherent complexity and heterogeneity of solid tumors. Here, we argue that, in many cases, it is the altered communication within the tumor, rather than mutations per se, that is the defining characteristic of cancer. As a result, tumorigenesis can be indirectly initiated by environmental or inherited factors that affect the stromal cells. We propose that anticancer research might be more effective if aimed at eradicating the cause of abnormality rather than just treating the end result.

Animals↗
PubMed2001

Putting tumours in context.

The interactions between cancer cells and their micro- and macroenvironment create a context that promotes tumour growth and protects it from immune attack. The functional association of cancer cells with their surrounding tissues forms a new 'organ' that changes as malignancy progresses. Investigation of this process might provide new insights into the mechanisms of tumorigenesis and could also lead to new therapeutic targets.

Animals↗
PubMed1998

Chloride is an allosteric effector of copper assembly for the yeast multicopper oxidase Fet3p: an unexpected role for intracellular chloride channels.

GEF1 is a gene in Saccharomyces cerevisiae, which encodes a putative voltage-regulated chloride channel. gef1 mutants have a defect in the high-affinity iron transport system, which relies on the cell surface multicopper oxidase Fet3p. The defect is due to an inability to transfer Cu+ to apoFet3p within the secretory apparatus. We demonstrate that the insertion of Cu into apoFet3p is dependent on the presence of Cl-. Cu-loading of apoFet3p is favored at acidic pH, but in the absence of Cl- there is very little Cu-loading at any pH. Cl- has a positive allosteric effect on Cu-loading of apoFet3p. Kinetic studies suggest that Cl- may also bind to Fet3p and that Cu+ has an allosteric effect on the binding of Cl- to the enzyme. Thus, Cl- may be required for the metal loading of proteins within the secretory apparatus. These results may have implications in mammalian physiology, as mutations in human intracellular chloride channels result in disease.

Allosteric Regulation↗