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At least 289 records · Page 16Linked to original sources
PubMed2003

The laminin receptor modulates granulocyte-macrophage colony-stimulating factor receptor complex formation and modulates its signaling.

Basement membrane matrix proteins are known to up-regulate granulocyte-macrophage colony-stimulating factor (GM-CSF) signaling in neutrophils and mononuclear phagocytes, but the mechanisms involved are poorly understood. We used the intracellular portion of the alpha subunit of the GM-CSF receptor (alphaGMR) to search for interacting proteins and identified the 67-kDa laminin receptor (LR), a nonintegrin matrix protein receptor expressed in several types of host defense cells and certain tumors, as a binding partner. LR was found to interact with the beta subunit of the GMR (betaGMR) as well. Whereas GM-CSF functions by engaging the alphaGMR and betaGMR into receptor complexes, LR inhibited GM-CSF-induced receptor complex formation. Laminin and fibronectin binding to LR was found to prevent the binding of betaGMR to LR and relieved the LR inhibition of GMR. These findings provide a mechanistic basis for enhancing host defense cell responsiveness to GM-CSF at transendothelial migration sites while suppressing it in circulation.

Base Sequence↗
PubMed1994

Modulation of H+-ATPase Activity by Fusicoccin in Plasma Membrane Vesicles from Oat (Avena sativa L.) Roots (A Comparison of Modulation by Fusicoccin, Trypsin, and Lysophosphatidylcholine).

The fungal phytotoxin fusicoccin affects various transport processes in the plasma membrane of plant cells. The plasma membrane (PM) H+-ATPase (EC 3.6.1.35) seems to be the primary target of fusicoccin action. The kinetics of the stimulation of the PM H+-ATPase by fusicoccin was studied in PM vesicles isolated from oat (Avena sativa cv Adamo) roots by aqueous two-phase partitioning. Considerable stimulation of activity was observed only when roots were treated with fusicoccin prior to the PM isolation. Fusicoccin treatment shifted the pH optimum of the ATPase toward more alkaline values and increased Vmax. No effects on Km were observed. Treatment with trypsin resulted in stimulation of ATPase activity in control vesicles but not in the fusicoccin-treated vesicles. The characteristics of stimulation by trypsin in control vesicles were comparable with those of stimulation by fusicoccin. This result and the change of the polypeptide pattern on western blots suggest the involvement of the C-terminal inhibitory domain in the fusicoccin signal transduction chain. On the other hand, stimulation by lyso-PC demonstrated other characteristics than stimulation by fusicoccin. Lyso-PC was able to stimulate ATPase activity at both acidic and alkaline pH values. Kinetic analysis of the pH dependency curves revealed different mechanisms for activation by fusicoccin and by lyso-PC. Whereas fusicoccin shifted the pH dependency of formation of phosphorylated intermediate to more alkaline values, lyso-PC seemed to increase dephosphorylation independently of pH.

Journal Article↗
PubMed1995

Vanadate inhibition of hepatocytic autophagy. Calcium-modulated and osmolality-modulated antagonism by asparagine.

The phosphate analogue vanadate, at 10 mM, strongly (approximately 90%) inhibited the autophagic sequestration of endogenous lactate dehydrogenase in isolated rat hepatocytes. The effect of vanadate was markedly (approximately 80%) antagonized by asparagine (20 mM), and to a lesser extent by glutamine, glycine, and alanine. The antagonism was only observed in the presence of Ca2+ when an isotonic standard incubation medium was used, but by increasing the medium osmolality this Ca2+ requirement could be eliminated. Asparagine induced a cell swelling (17% at 20 mM) that might account for at least part of its vanadate antagonism, since hypotonic cell swelling by itself stimulated autophagy (with a maximal effect at approximately 200 mosM). Conversely, hypertonic media inhibited autophagy and were additive to vanadate. In a strongly hypotonic medium (less than 200 mosM), both asparagine and vanadate were inhibitory. However, since vanadate alone had no effect on cell volume, the vanadate-asparagine antagonism could not be exerted exclusively at the level of cell volume regulation. An additional mechanism might be a partial deamination of asparagine, generating ammonia, which was found to oppose the vanadate inhibition of autophagy while having no effect on cell volume. Other metabolizable amino acids, like alanine and glycine, were moderately vanadate-antagonistic while failing to induce cell swelling. These results are compatible with a vanadate-antagonistic effect of asparagine mediated partly through an unknown mechanism (possibly pH change) by its deamination product, ammonia, partly through cell swelling and a secondary Ca2+ influx that could compensate for a vanadate-induced depletion of intracellular calcium stores.

Adenosine Triphosphate↗
PubMed1995

Perceptual organization in a comodulation masking release interference paradigm: exploring the role of amplitude modulation, frequency modulation, and harmonicity.

Two areas of interest within auditory scene analysis are the identification of cues which contribute to auditory grouping and/or segregation, and the methodology employed to measure such effects. The present study explored the roles of three purported grouping cues--correlated AM, correlated FM, and harmonicity--using a comodulation masking release interference paradigm. This method was reasoned to be free of alterations in the subject's mode of listening (analytic versus synthetic). The results suggested that correlated AM was a viable grouping cue. For some listeners, the presence of FM also appeared to provide a grouping cue, but, generally, no effect of coherence of FM was observed. No effect of harmonicity was observed in this paradigm.

Adult↗