A mechanism for regulation of the adhesion-associated proteintyrosine kinase pp125FAK

Focal adhesion kinase (pp125FAK) is a member of a growing family of structurally distinct protein tyrosine kinases that includes the recently identified FakB and PYK2/CAKbeta/RAFTK. Activation of pp125FAK has been functionally linked to the formation of focal adhesions, integrin-mediated sites of contact between the cell and the extracellular matrix. The carboxy-terminal domain of pp125FAK is also expressed as a separate protein called pp41/43FRNK (where FRNK represents pp125FAK-related non-kinase). Here we show that pp41/43FRNK acts as an inhibitor of pp125FAK by transiently blocking the formation of focal adhesions on fibronectin and constitutively reducing tyrosine phosphorylation of both pp125FAK and two focal adhesion proteins, tensin and paxillin. These inhibitory effects of pp41/43FRNK are reversed by co-expression of pp125FAK, suggesting that pp125FAK and pp41/43 FRNK compete for a common binding protein(s) whose association with pp125FAK is necessary for signalling by pp125FAK. We propose that pp41/43FRNK functions as an endogenous regulator of pp125FAK, thus providing an unusual means to regulate both tyrosine kinase activity and cellular adhesion to the extracellular matrix.

Association of phosphatidylinositol 3-kinase, via the SH2 domains of p85, with focal adhesion kinase in polyoma middle t-transformed fibroblasts

Focal adhesion kinase (FAK), a non-receptor protein tyrosine kinase, becomes activated and phosphorylated on tyrosine in cells transformed with v-src. By cytoimmunofluorescence a sub-fraction of the p85 subunit of phosphoinositide 3-kinase (PI 3-kinase) localized in focal adhesion plaques. We examined the possibility that FAK associates with PI 3-kinase. In fibroblasts transformed with polyoma middle t, PI 3-kinase activity co-immunoprecipitated with pp125FAK using two different antibodies against this protein. PP125FAK from middle t-transformed cells associated with a glutathione-S-transferase fusion protein containing the 85-kDa subunit of phosphatidylinositol 3-kinase. Both of the SH2 domains and the SH3 domain of p85 also formed complexes with pp125FAK in vitro. Phosphopeptides that bind to the SH2 domains completely blocked the binding of full-length p85 to pp125FAK, while a peptide that binds to the SH3 domain was ineffective, indicating that the association between p85 and pp125FAK is mediated by the SH2 domains of p85.

Psychosis and genes with trinucleotide repeat polymorphism

Abnormal expansion of genes with trinucleotide repeat (TNR) polymorphism has been found in a number of neuropsychiatric disorders. These disorders and the major psychoses, schizophrenia and bipolar affective disorder, appear to share an interesting phenomenon: genetic anticipation. Because TNR expansion correlates with anticipation, these unstable DNA sites are considered important candidate loci for the major psychoses. We investigated genes with TNR polymorphisms, including B1, B33, B37, and the N-cadherin gene, in unrelated Caucasian North American and Italian schizophrenics (n = 53 to 74), and matched controls. Also, unrelated Caucasian North American patients with bipolar I affective disorder were screened for the B33 and N-cadherin genes (n = 49 and 63, respectively). No unusually long alleles that would suggest abnormal expansion of the TNR were observed for any of these genes. Also, no statistically significant results were found in tests for genetic association between any of these genes and schizophrenia. For B37, a trend toward a difference in allele counts between schizophrenics and controls was observed. However, no clear evidence for a role of these TNR-containing genes in schizophrenia or bipolar affective disorders was found.

Identification and characterization of an iron-regulated hemopexin receptor in Haemophilus influenzae type b

Heme can serve Haemophilus influenzae as a source of both essential porphyrin and iron. In extracellular mammalian body fluids neither free heme nor free iron is available, since they are tightly bound to hemopexin and transferrin, respectively. Since H. influenzae grows in the presence of iron-transferrin and heme-hemopexin and is known to express a saturable receptor for transferrin, we investigated the process by which this pathogen acquired heme from hemopexin for use as an iron source. The ability of human and rabbit hemopexin to donate heme as a source of iron to H. influenzae type b strains was demonstrated by plate bioassays. With a dot enzyme assay with biotinylated hemopexin as ligand, H. influenzae bound heme-hemopexin and apo-hemopexin following growth in iron-restricted, but not in iron-sufficient, medium. Competitive binding studies with heme-hemopexin and apo-hemopexin demonstrated saturability of binding. Neither heme, protoporphyrin IX, hemoglobin, nor transferrin blocked the binding of hemopexin to whole cells, demonstrating the specificity of binding. Treatment of whole H. influenzae cells with trypsin abolished binding. Taken together, these observations suggest that H. influenzae type b expresses an outer membrane protein(s) which acts as a receptor for hemopexin and which is regulated by the availability of iron in the growth medium. In iron-restricted media, H. influenzae 706705 and DL42 did not express the 100-kDa hemopexin-binding protein previously reported (M.S. Hanson, S.E. Pelzel, J. Latimer, U. Muller-Eberhard, and E.J. Hansen, Proc. Natl. Acad. Sci. USA 89:1973-1977, 1992). The putative iron-regulated hemopexin receptor was solubilized from cell envelopes of H. influenzae 706705, DL42, and Eagan with the detergent CHAPS (3-[(3-cholamidopropyl)-dimethyl-ammonio]-1-propanesulfonate) and isolated by affinity chromatography on heme-hemopexin-Sepharose 4B. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the proteins bound to the affinity resin revealed three proteins of 29, 38, and 57 kDa, of which the 57- and 29-kDa proteins bound hemopexin after Western blotting (immunoblotting). A monoclonal antibody to the 57-kDa hemopexin-binding protein of 706705 recognized a 57-kDa protein on Western blots of the cell envelope proteins of 706705, DL42, and Eagan; no reaction was observed with the 100-kDa hemopexin-binding protein of DL42. These data suggest that some H. influenzae strains possess at least two hemopexin receptors, the expression of which is determined by the prevailing growth environment.

A recombinant amino terminal fragment of bactericidal/permeability-increasing protein inhibits the induction of leukocyte responses by LPS

Bactericidal/permeability-increasing protein (BPI) is a major component of the granules of polymorphonuclear neutrophils (PMNs) and is involved in the killing of gram-negative bacteria. A 23-kd recombinant protein, corresponding to the NH2-terminal fragment of human BPI (rBPI23), has been shown to bind lipid A and antagonize some lipopolysaccharide (LPS)-mediated effects. In this study the ability of rBPI23 to prevent a wide range of cellular responses to LPS was investigated. In vitro assays were carried out using human blood to more closely approximate in vivo conditions. The release of proinflammatory cytokines [tumor necrosis factor (TNF), interleukin-1 beta (IL-1 beta), IL-6, IL-8], induced by E. coli O113 LPS, was markedly reduced by rBPI23 in a concentration-dependent fashion. The production of the anti-inflammatory protein IL-1ra (IL-1 receptor antagonist) was triggered by lower LPS concentrations than those necessary for the other cytokines. Furthermore, prevention of IL-1ra release required higher rBPI23 concentrations than for other cytokines. The LPS-induced production of oxygen-derived free radicals by phagocytic cells (resulting in chemiluminescence) was also prevented by rBPI23. The inhibition was specific for LPS because the activation of leukocytes by phorbol myristate acetate, zymosan, or TNF was unaffected by BPI. The ability of rBPI23 to antagonize specifically the effects of endotoxin in the complex environment of human blood along with its bactericidal activity suggests that rBPI23 may be a novel therapeutic agent in the treatment of gram-negative infections.

Antigenic relationships of transferrin-binding proteins from Neisseria meningitidis, N. gonorrhoeae and Haemophilus influenzae: cross-reactivity of antibodies to NH2-terminal peptides

The NH2-terminal amino sequence through the first 20 amino acids was obtained for transferrin-binding protein (TBP)1 from three strains of Neisseria meningitidis. These were identical except for a glutamine to a glycine substitution at residue 6 in one case. The sequences of the NH2-terminal 20 amino acids of TBP2 from the same three strains were also determined; one TBP2 had a M(r) of 68,000 and the other two of 78,000. Sequences were identical up to residue 13 in all three proteins. Peptides based on the NH2-terminal sequences of TBP1 and 2 were synthesized, linked to Keyhole Limpet haemocyanin and used to raise antibodies in rabbits. Anti-peptide antibodies cross-reacted on immunoblotting with the respective TBPs from all meningococcal strains tested, as well as with those from N. gonorrhoeae, suggesting that the NH2-terminals of these proteins are well conserved in the Neisseria. Neither anti-peptide serum reacted with the analogous TBP1 and 2 from Haemophilus influenzae, although common epitopes have previously been shown to exist.

High-affinity binding of the bactericidal/permeability-increasing protein and a recombinant amino-terminal fragment to the lipid A region of lipopolysaccharide

Bactericidal/permeability-increasing protein (BPI) is a 55-kDa cationic protein (nBPI55) elaborated by polymorphonuclear neutrophils (PMN). BPI has potent bactericidal activity against a wide variety of gram-negative organisms and neutralizes endotoxin activities. An N-terminal fragment of nBPI55 exhibits the bactericidal and antiendotoxin properties of the holoprotein. To further characterize the biological activities of the N-terminal fragment, a recombinant protein (rBPI23) corresponding to the first 199 amino acids of human BPI was produced and purified. rBPI23 had antibacterial activity equivalent to that of nBPI55 against Escherichia coli J5. Furthermore, both rBPI23 and nBPI55 bound identically to a broad range of R- and S-form lipopolysaccharides (LPS) and to natural and synthetic lipid A. Binding of radiolabeled nBPI55 to LPS was inhibited in an identical fashion by either nBPI55 or rBPI23. The binding of both proteins to immobilized E. coli J5 lipid A was inhibited in a comparable fashion by long- or short-chain LPS or lipid A. The binding of both rBPI23 and nBPI55 was specific, saturable, and of high affinity, with an apparent Kd of approximately 2 to 5 nM for all ligands tested. These results demonstrate that BPI recognizes the highly conserved lipid A region of bacterial LPS via residues contained within the amino-terminal portion of the BPI molecule.

The Role of Magma Overpressure in Suppressing Earthquakes and Topography: Worldwide Examples

In an extending terrane basaltic magma supplied at a pressure greater than the least principal stress (overpressure) may be capable of suppressing normal faulting and the earthquakes and topographic relief that commonly accompany normal faulting. As vertical dikes intrude, they press against their walls in the direction opposite the least principal stress and increase its magnitude. The emplacement of tabular intrusions causes the internal magma pressure to act selectively in opposition to tectonic stresses. This process tends to equalize the stresses and thus diminishes the deviatoric stress (difference between maximum and minimum stresses) that creates faults and causes earthquakes. Observations of the pattern of seismicity and magmatism worldwide indicate that magmatism commonly supplants large earthquakes as the primary mechanism for accommodating tectonic extension. Recognizing the extent of magmatic stress accommodation is important in assessing seismic and volcanic risks.

Effects of norepinephrine on neonatal rat cardiocyte growth and differentiation

Norepinephrine stimulates the growth in size of nondividing neonatal cardiocytes. During this time the neonatal cardiocyte is in a period of transition in which the cell can synthesize DNA and yet does not divide. Because the cell undergoes karyokinesis without cytokinesis the objective of this study was to determine whether the norepinephrine-induced growth in size of the neonatal cardiocyte was accompanied by an increase in a) the number of cardiocytes synthesizing DNA, b) the number of binucleate cardiocytes, and c) organized myofibrils. One- to four-d-old neonatal rat heart cells were isolated and placed in serum-free medium which was then supplemented with serum, norepinephrine, norepinephrine plus propranolol, or isoproterenol. After 4 d the number and size of the cells was determined using a Coulter counter. In other cultures cardiocytes were fixed on Days 0, 1, 2, and 4, and an increase in the number of binucleate cardiocytes was found in all treatment groups including controls. However, the rate of binucleation was faster in the norepinephrine group. It was also determined by proliferating cell nuclear antigen (PCNA) antibody staining that by Day 4, over 50% of the cardiocytes were in the cell cycle. The percentage of cells in which PCNA could be detected was higher in the norepinephrine and norepinephrine plus propranolol groups. Furthermore, there was a concomitant increase in the amount and organization of myofibrils in the catecholamine-treated cardiocytes.

Electrophysiology versus psychophysics in the detection of visual loss in pseudotumor cerebri

This study compared visual evoked potentials (VEP) and contrast sensitivity (CS) as methods of detecting visual loss in 15 women with acute onset of pseudotumor cerebri (PTC). A total of 24 out of 30 eyes (14 of 15 patients) had a visual disturbance. Neuro-ophthalmologic examination demonstrated abnormal Goldmann visual fields in 13 of 30 eyes. CS was abnormal in 18 eyes; VEP was abnormal in five eyes. Nine eyes had visual loss detected by CS only, five by perimetry only, and one had the VEP as the sole abnormality. CS was a valuable adjunct to perimetry in PTC whereas VEP was rarely helpful.

Properties of cultured endothelium from adult human vessels

Endothelium was isolated from samples of aorta and vena cava obtained from cadaver donors at the time kidneys were harvested for transplantation. Digestion with collagenase and gentle swabbing were used to free the cells from the intimal surface. Low density seeding permitted isolation of individual colonies with typical endothelial morphology. Modified Medium 199 supplemented with 10%-20% human plasma-derived serum and an extract from the bovine hypothalamus (500 micrograms/ml) enabled subcultured colonies to grow to confluency when culture surfaces were coated with fibronectin (1 micrograms/cm2). The presence of Factor VIII antigen was demonstrated using an indirect immunofluorescence technique. A monoclonal antibody to cultured umbilical vein endothelium, specific for endothelium, reacted with the subcultured cells from the aorta and vena cava. Type IV procollagen, fibronectin, and thrombospondin were identified as labeled proteins secreted by cultures of adult endothelium that had been incubated with 3H-proline and 3H-glycine. When the cultured endothelium was used in a sodium-m-periodate stimulated T lymphocyte mitogenic culture system, the endothelium exhibited accessory cell function. Prostacyclin production stimulated by incubation with arachidonic acid and PGH2 was variable from vessel to vessel. However, average values were lower than normally seen with cultured primary umbilical vein endothelium.

Metabolic labeling of lutropin with [35S]sulfate

Chemical analyses have previously detected sulfate linked to the oligosaccharides of lutropin isolated from bovine and human pituitaries. To determine whether lutropin could be metabolically labeled with sulfate, isolated bovine and rat pituitaries were incubated with [35S]sulfate. In both species, two major labeled products were immunoprecipitated with antisera specific to lutropin subunits. Incorporation into the subunits occurred posttranslationally since it was not blocked by cycloheximide, which did, however, block the incorporation of radiolabeled methionine. Metabolic labeling with [35S]sulfate provides a valuable approach for examining the biosynthetic processing of lutropin and the physiological role of sulfate in this hormone.

Effect of two days' monotonous confinement on conditioned eyelid frequency and topography

Conditioned discriminative eyelid response frequency and topography for 9 Ss was compared before, immediately after and 2 to 7 days following 2 days of monotonous confinement. Monotonous confinement did not enhance learning over control readings; however, it may have a selective effect on individual differences and conditioning.