Biomedical subjects

I Caras

Publications and source records attributed to I Caras.

6 recordsLinked to original sources

PubMed2000

Regulation of elastinolytic cysteine proteinase activity in normal and cathepsin K-deficient human macrophages.

Human macrophages mediate the dissolution of elastic lamina by mobilizing tissue-destructive cysteine proteinases. While macrophage-mediated elastin degradation has been linked to the expression of cathepsins L and S, these cells also express cathepsin K, a new member of the cysteine proteinase family whose elastinolytic potential exceeds that of all known elastases. To determine the relative role of cathepsin K in elastinolysis, monocytes were differentiated under conditions in which they recapitulated a gene expression profile similar to that observed at sites of tissue damage in vivo. After a 12-d culture period, monocyte-derived macrophages (MDMs) expressed cathepsin K in tandem with cathepsins L and S. Though cysteine proteinases are acidophilic and normally confined to the lysosomal network, MDMs secreted cathepsin K extracellularly in concert with cathepsins L and S. Simultaneously, MDMs increased the expression of vacuolar-type H(+)-ATPase components, acidified the pericellular milieu, and maintained extracellular cathepsin K in an active form. MDMs from a cathepsin K-deficient individual, however, retained the ability to express, process, and secrete cathepsins L and S, and displayed normal elastin-degrading activity. Thus, matrix-destructive MDMs exteriorize a complex mix of proteolytic cysteine proteinases, but maintain full elastinolytic potential in the absence of cathepsin K by mobilizing cathepsins L and S.

Cathepsin B↗

PubMed1999

Regional differences in the developing cerebral cortex revealed by ephrin-A5 expression.

The development of axonal connections between thalamic nuclei and their cortical target areas occurs in a highly specific manner. To explore the mechanisms of thalamocortical axon pathfinding, we investigated the expression of several members of the ephrin and Eph gene families in the forebrain. The Eph ligand ephrin-A5 was expressed in three distinct gradients during the development of the telencephalon. The first gradient occurred in the cortical ventricular zone and established ephrin-A5 as one of the earliest markers distinguishing cells residing in the anterior versus posterior cortical neuroepithelium. The second gradient was apparent in the subplate and occurred in spatial opposition to a distinct gradient for the low-affinity NGF receptor p75. This finding reveals that different regions of the early subplate are molecularly heterogeneous. Third, we confirmed that ephrin-A5 is expressed in a bi-directional gradient in the cortical plate, with highest levels in the somatomotor cortex. Three putative receptors for ephrin-A5 -- EphA3, EphA4 and EphA5 -- showed distinct expression patterns in the developing thalamus. The graded distributions of ephrin-A5 in the developing subplate and cortex and the expression of its receptors in the thalamus are consistent with the notion that the Eph ligands and their receptors may function in the topographic mapping of thalamic axons to specific cortical areas.

Animals↗

PubMed1998

Protein targeting in the analysis of learning and memory: a potential alternative to gene targeting.

Gene targeting using homologous recombination in embryonic stem (ES) cells offers unprecedented precision with which one may manipulate single genes and investigate the in vivo effects of defined mutations in the mouse. Geneticists argue that this technique abrogates the lack of highly specific pharmacological tools in the study of brain function and behavior. However, by now it has become clear that gene targeting has some limitations too. One problem is spatial and temporal specificity of the generated mutation, which may appear in multiple brain regions or even in other organs and may also be present throughout development, giving rise to complex, secondary phenotypical alterations. This may be a disadvantage in the functional analysis of a number of genes associated with learning and memory processes. For example, several proteins, including neurotrophins--cell-adhesion molecules--and protein kinases, that play a significant developmental role have recently been suggested to be also involved in neural and behavioral plasticity. Knocking out genes of such proteins may lead to developmental alterations or even embryonic lethality in the mouse, making it difficult to study their function in neural plasticity, learning, and memory. Therefore, alternative strategies to gene targeting may be needed. Here, we suggest a potentially useful in vivo strategy based on systemic application of immunoadhesins, genetically engineered fusion proteins possessing the Fc portion of the human IgG molecule and, for example, a binding domain of a receptor of interest. These proteins are stable in vivo and exhibit high binding specificity and affinity for the endogenous ligand of the receptor, but lack the ability to signal. Thus, if delivered to the brain, immunoadhesins may specifically block signalling of the receptor of interest. Using osmotic minipumps, the protein can be infused in a localized region of the brain for a specified period of time (days or weeks). Thus, the location and timing of delivery are controlled. Here, we present methodological details of this novel approach and argue that infusion of immunoadhesins will be useful for studying the role particular receptors play in behavioral and neural plasticity.

Animals↗

PubMed1989

Effects of O-linked glycosylation on the cell surface expression and stability of decay-accelerating factor, a glycophospholipid-anchored membrane protein.

Decay accelerating factor (DAF) is a glycophospholipid-anchored membrane glycoprotein that protects mammalian host cells from inadvertant complement lysis. The effects of inhibiting mucin-type O-glycosylation on the cell surface expression of DAF were studied by introducing an expression vector for human DAF into wild-type Chinese hamster ovary and ldlD cells. The ldlD cells express reversible defects in the addition of galactose and N-acetylgalactosamine (GalNAc) to oligosaccharide chains on glycoproteins and glycolipids. Mucin-type O-glycosylation of proteins is inhibited in ldlD cells and can be selectively corrected by the addition of GalNAc to the culture medium. The attachment of a phosphatidylinositol phospholipase C-sensitive glycolipid anchor to DAF and its efficient sorting to the cell surface in ldlD cells were independent of galactose and GalNAc additions to glycolipids and proteins. Attachment of galactose and GalNAc to DAF's glycolipid anchor were apparently not required for its normal function. However, in the absence of O-glycosylation DAF was proteolytically cleaved soon after reaching the cell surface, and a large fragment of DAF was released into the culture medium. This rapid proteolysis/release resulted in the expression of very low steady state levels of O-glycosylation-deficient DAF as measured by immunoblotting. These results, in conjunction with those obtained from studies of three other membrane glycoproteins expressed in ldlD cells, suggest that O-linked sugars on membrane glycoproteins may frequently play a role in determining the level of cell surface expression of these proteins.

Acetylgalactosamine↗

PubMed1988

The structural gene for the M1 subunit of ribonucleotide reductase maps to chromosome 11, band p15, in human and to chromosome 7 in mouse.

The genes for the M1 subunit of the enzyme ribonucleotide reductase have been mapped in the human and the murine species by use of two independently derived mouse cDNA clones. Southern blot analysis of rodent x human somatic cell hybrid DNAs confirmed the assignment of RRM1 to the short arm of human chromosome 11. In situ hybridization to human metaphase chromosomes revealed a peak of silver grains over the distal third of band 11p15, a region corresponding to subbands p15.4----p15.5. The mouse Rrml locus was assigned to chromosome 7, where it forms part of a conserved syntenic group of at least seven other genes assigned to human chromosome band 11p15.

Animals↗

PubMed1975

Partial purification and properties of microsomal phosphatidate phosphohydrolase from rat liver.

Microsomal phosphatidate phosphohydrolase (phosphatidate phosphatase EC 3.1.3.4) was solubilized and fractionated to yield at least two distinct enzymatically active fractions. One, denoted FA, was non-specific, had a relatively high Km for phosphatidic acid and was insensitive to inhibition by diacylglycerol. The second fraction, FB, was specific for phosphatidates, had a low Km, and was inhibited, non-competitively, by diacylglycerol. FA exhibited a sigmoid substrate-activity curve. The isolated FB aggregated to particles of about 10(6) in the absence of salts and could be dissociated by the addition of monovalent cations at ionic strength 0.4-0.6 to about 2-10(5) daltons and thereby doubled its activity. Dissociation was time- and temperature-dependent. F- was inhibitory. Divalent ions were not required for the activity of FA or FB and inhibited at concentrations exceeding 1 mM.

Animals↗