Publications by authors named "Chunbo Qin"

The goal was to examine whether visuomotor control and choice response time shared age-related developmental trajectories, and if prior computer experience played an important role in control processes. Children (6-7, 8-9, 10-11 yr.), younger adults (24 yr.

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Objective: Interaction of macrophages with aggregated matrix-anchored lipoprotein deposits is an important initial step in atherogenesis. Aggregated lipoproteins require different cellular uptake processes than those used for endocytosis of monomeric lipoproteins. In this study, we tested the hypothesis that engagement of aggregated LDL (agLDL) by macrophages could lead to local increases in free cholesterol levels and that these increases in free cholesterol regulate signals that control cellular actin.

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Objective: Atherogenesis begins as small subendothelial accumulations of foam cells that develop through unregulated uptake of modified and aggregated low-density lipoprotein (LDL). The reason why foam cells remain in the atherosclerotic plaque rather than migrating out of the area is unclear. We tested the hypothesis that elevated membrane cholesterol levels, which may result from interactions with aggregated LDL, affect macrophage migration.

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The phospholipase D (PLD) family of Arabidopsis thaliana has 12 identified members, including three highly homologous PLDgammas. The enzymatic and molecular properties of PLDgamma2 were characterized and compared with those of PLDgamma1. Two variants of PLDgamma2 cDNAs, designated PLDgamma2a and PLDgamma2b, were isolated, and they differ in the presence of a 96-nucleotide fragment at the beginning of the open reading frame.

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The mammalian ATP-binding cassette transporters A1 and A7 (ABCA1 and -A7) show sequence similarity to CED-7, a Caenorhabditis elegans gene that mediates the clearance of apoptotic cells. Using RNA interference or gene targeting, we show that knock down of macrophage ABCA7 but not -A1 results in defective engulfment of apoptotic cells. In response to apoptotic cells, ABCA7 moves to the macrophage cell surface and colocalizes with the low-density lipoprotein receptor-related protein 1 (LRP1) in phagocytic cups.

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Root elongation and root hair formation are important in nutrient absorption. We found that two Arabidopsis (Arabidopsis thaliana) phospholipase Ds (PLDs), PLDzeta1 and PLDzeta2, were involved in root elongation during phosphate limitation. PLDzeta1 and PLDzeta2 are structurally different from the majority of plant PLDs by having phox and pleckstrin homology domains.

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Objective: During atherogenesis, macrophages migrate into the subendothelial space where they ingest deposited lipoproteins, accumulate lipids, and transform into foam cells. It is unclear why these macrophages do not remove their lipid loads from the region. This study was aimed at testing the hypothesis that macrophage behavior is altered when membrane cholesterol levels are elevated, as might be the case for cells in contact with lipoproteins within atherosclerotic lesions.

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Phospholipase D (PLD) and protein phosphatase 2C (PP2C) both play a role in mediating plant responses to abscisic acid (ABA). In this article, we show that PLD alpha 1 and its product, phosphatidic acid (PA), regulate a PP2C, ABI1, which is a negative regulator of ABA responses in Arabidopsis. Leaves from a T-DNA insertional mutant of PLD alpha 1 and PLD alpha 1-antisense plants lose more water than do wild-type plants.

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Hydrolysis of common membrane phospholipids occurs in response to various environmental stresses, but the control and cellular function of this hydrolysis are not fully understood. Hydrogen peroxide (H2O2) is a pivotal signaling molecule involved in various stress responses. Here, we show that the plasma membrane-bound phospholipase D, PLDdelta, is activated in response to H2O2 and that the resulting phosphatidic acid (PA) functions to decrease H2O2-promoted programmed cell death.

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Phospholipase D (PLD) enzymes from bacteria to mammals exhibit a highly conserved core structure and catalytic mechanism, but whether protein-protein interactions exhibit similar commonality is unknown. Our objective was to determine whether the physical and functional interactions of mammalian PLDs with actin are evolutionarily conserved among bacterial and plant PLDs. Highly purified bacterial and plant PLDs cosedimented with mammalian skeletal muscle alpha-actin, indicating direct interaction with F-actin.

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Phospholipase D (PLD) is a major plant phospholipase family involved in many cellular processes such as signal transduction, membrane remodeling, and lipid degradation. Five classes of PLDs have been identified in Arabidopsis thaliana, and Ca(2+) and polyphosphoinositides have been suggested as key regulators for these enzymes. To investigate the catalysis and regulation mechanism of individual PLDs, surface-dilution kinetics studies were carried out on the newly identified PLDdelta from Arabidopsis.

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Phospholipases are activated in response to various cellular and environmental cues. Their activation can affect many cellular processes through their roles in signal transduction. Recent advances in the biochemical and molecular understanding of phospholipase D (PLD) have provided insights into potential networks of PLDs and other phospholipases in plants.

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Four types of phospholipase D (PLD), PLD alpha, beta, gamma, and delta, have been characterized in Arabidopsis, and they display different requirements for Ca(2+), phosphatidylinositol 4,5-bisphosphate (PIP(2)), substrate vesicle composition, and/or free fatty acids. However, all previously cloned plant PLDs contain a Ca(2+)-dependent phospholipid-binding C2 domain and require Ca(2+) for activity. This study documents a new type of PLD, PLD zeta 1, which is distinctively different from previously characterized PLDs.

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