Localization of phospholipase D in detergent-insoluble, caveolin-rich membrane domains. Modulation by caveolin-1 expression and caveolin-182-101

The activation of cellular phospholipase D (PLD) is implicated in vesicular trafficking and signal transduction. Two mammalian PLD forms, designated PLD1 and PLD2, have been cloned, but their cellular localization and function are not fully understood. Here, we report that in HaCaT human keratinocytes, as well as other cell lines, PLD activity is highly enriched in low density, Triton X-100-insoluble membrane domains that contain the caveolar marker protein caveolin-1. Similar to other PLDs, the PLD activity in these membrane domains is stimulated by phosphatidylinositol 4, 5-bisphosphate and is inhibited by neomycin. Immunoblot analysis indicated that caveolin-rich membrane domains do not contain the PLD1 isoform. Stable transfection of mouse PLD2 in Chinese hamster ovary cells greatly increased PLD activity in these domains compared with PLD activity in control Chinese hamster ovary cells transfected with vector alone. PLD activity is enriched in low density Triton-insoluble membrane domains also in U937 promonocytes, even though these cells do not express caveolin-1. In U937 cells, also, PLD1 is largely excluded from low density Triton-insoluble membrane domains. Expression of recombinant caveolin-1 in v-Src-transformed NIH-3T3 cells resulted in up-regulation of PLD activity in the caveolin-containing membrane domains. The caveolin scaffolding peptide (caveolin-182-101) modulated the caveolar PLD activity, causing stimulation at concentration of 1-10 microM and inhibition at concentrations >10 microM. We conclude that a PLD activity, which is likely to represent PLD2, is enriched in low density Triton-insoluble membrane domains. The effects of caveolin-1 expression and of the caveolin scaffolding peptide suggest that in cells that express caveolin-1, PLD may be targeted to caveolae. The possible functions of PLD in the dynamics of caveolae and related domains and in signal transduction processes are discussed.     

Spectroscopic Studies of d-Pilocarpine and Some Quaternary Derivatives

Detailed spectroscopic studies have been carried out on the alkaloid d-pilocarpine as free base and after quaternization. Characteristic changes in the NMR, IR and UV spectroscopic properties have been established following quaternization. The respective mass spectra have been analysed, and characteristic fragmentation patterns are described. The amidic nature of d-pilocarpinehydroxamic acid has been confirmed by IR, NMR and mass spectrometric measurement.     

Studies on the C–H/C–D Exchange in Imidazolium (Pilocarpinium) and in 2- and 4-Hydroximinomethyl Pyridinium Compounds

The H–D exchange of methylene protons in a side-chain when situated between a positively charged N-atom (α–CH₂) and a ketone function was studied in various pilocarpinium (N-methyl imidazolium) and hydroximinomethyl pyridiniums using NMR measurements. Structural factors which determine the course of the exchange are reported, and the role of the solvent was examined. Mass-spectra of nondeuteriated and deuteriated 4-hydroximinomethyl-1-phenacyl-pyridinium chloride confirmed the fast exchange of the α–CH_a. An alternative H–D exchange of the C₂–H in the imidazolium moiety of certain pilocarpinium compounds without a ketone in the N-chain was detected. Mechanisms for the two types of exchanges involving an ylid as intermediate and attack of a deuteron were proposed.     

Attentional capture by irrelevant emotional distractor faces.

We establish attentional capture by emotional distractor faces presented as a “singleton” in a search task in which the emotion is entirely irrelevant. Participants searched for a male (or female) target face among female (or male) faces and indicated whether the target face was tilted to the left or right. The presence (vs. absence) of an irrelevant emotional singleton expression (fearful, angry, or happy) in one of the distractor faces slowed search reaction times compared to the singleton absent or singleton target conditions. Facilitation for emotional singleton targets was found for the happy expression but not for the fearful or angry expressions. These effects were found irrespective of face gender and the failure of a singleton neutral face to capture attention among emotional faces rules out a visual odd-one-out account for the emotional capture. The present study thus establishes irrelevant, emotional, attentional capture. (PsycINFO Database Record (c) 2011 APA, all rights reserved)