Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0012739 (disseminated intravascular coagulation)
 8,673 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The interaction of the actin-binding protein hisactophilin from Dictyostelium discoideum amoebae to partially charged lipid membranes composed of mixtures of L-alpha-dimyristoylphosphatidylcholine (DMPC) with L-alpha-dimyristoylphosphatidylglycerol (DMPG) and L-alpha-phosphatidylinositol 4,5-bisphosphate (PIP2) is studied by film balance experiments, microfluorescence, and lateral diffusion measurements at low ionic strengths (approximately 20 mM). Excess surface concentrations and adhesion energies of the protein are evaluated by the application of Gibbs law of surface excess as a function of charged lipid content. Protein expressed in E. coli lacking a myristic acid chain (EC-HIS) and natural protein with a fatty acid (DIC-HIS) isolated from Dictyostelium cells are compared. For mixtures of DMPG and DMPC, protein binding leads to an increase in lateral pressure of the monolayer (at constant area) and causes strong lipid immobilization pointing to partial penetration of the protein into the lipid layer. The natural protein causes a much stronger immobilization than does EC-HIS. For a given bulk concentration, the adsorbed protein/lipid molar ratio increases with the molar fraction chi PG of charged lipid but saturates at about 50 mol% of DMPG. Natural hisactophilin (DIC-HIS) binding to PIP2-containing monolayers is purely electrostatic at low bulk concentration cb, and protein penetration dominates only at cb > 68 nM. Fluorescence experiments demonstrate that the natural protein (DIC-HIS) can mediate the binding of monomeric actin or very small oligomers to membranes, showing that the adsorbed protein remains functional. In contrast, the recombinant hisactophilin (EC-HIS) can mediate only the membrane coupling of larger actin structures.
 ...
PMID:The actin-binding protein hisactophilin binds in vitro to partially charged membranes and mediates actin coupling to membranes. 757 33

The neutron reflectivity technique is applied to determine the adsorptive interaction of the 13.5-kDa actin-binding protein hisactophilin from Dictyostelium discoideum with lipid monolayers at a lateral pressure of 21 mN/m < or = pi < or = 25 mN/m at the air-water interface. We compare binding of natural hisactophilin exhibiting a myristic acid chain membrane anchor at the N-terminus (DIC-HIS) and a fatty acid-deficient genetic product expressed in Escherichia coli (EC-HIS). It is demonstrated that only the natural hisactophilin DIC-HIS is capable of mediating the strong binding of monomeric actin to the monolayer, where it forms a layer of about 40 A thickness corresponding to the average diameter of actin monomers. Monolayers composed of pure dimyristoyl phosphatidylcholine with fully deuterated hydrocarbon tails and headgroup (DMPC-d67) and 1:1 mixtures of this lipid with chain deuterated dimyristoyl phosphatidylglycerol (DMPG-d54) are studied on subphases consisting either of fully deuterated buffer (D2O) or of a 9:1 H2O/D2O buffer that matches the scattering length density of air (CMA buffer). The reflectivity data are analyzed in terms of layer models, consisting of one to three layers, depending on the contrast of the buffer and the system. We show that both protein species bind tightly to negatively charged 1:1 DMPC-d67/DMPG-d54 monolayers, thereby forming a thin and most probably monomolecular protein layer of 12-15 A thickness. We find that the natural protein (DIC-HIS) partially penetrates into the lipid monolayer, in contrast to chain-deficient species (EC-HIS), which forms only an adsorbed layer. The coverage of the monolayer with DIC-HIS strongly depends on the presence of anionic DMPG in the monolayer. At a bulk protein concentration of 1.5 micrograms/ml, the molar ratio of bound protein to lipid is about 1:45 for the 1:1 lipid mixture but only 1:420 for the pure DMPC.
 ...
PMID:Hisactophilin-mediated binding of actin to lipid lamellae: a neutron reflectivity study of protein membrane coupling. 884 19

To date, protrusion of pseudopodia has been considered to be primarily responsible for translocation of free-living amoebae and leukocytes of higher organisms. Although there is little question that the pseudopodium plays an important role, little attention has been given to the cortical structures that are responsible for cell-substratum anchorage in amoeboid movement. Here, we report on a new knobby foot-like structure in amoebae of a cellullar slime mold, Dictyostelium discoideum. These feet, each about 1 micron in diameter, appear transiently in multiple units at the base of certain pseudopodia where the amoeba contacts a partially deformable substrate. The feet were discovered, and their spatial and temporal behavior relative to pseudopodial anchorage and invasive locomotion were observed, by examining Dictyostelium amoebae using a DIC video microscope providing an 0.3 micron depth of field. Key evidence for the anchoring role of the knobby feet was obtained by investigating amoebae, flattened in a specially devised observation chamber, and attracted by chemotaxis towards 3',5' cyclic-adenosine monophosphate (cAMP). The cAMP was released by highly localized, pulsed UV-microbeam irradiation of caged cAMP. We show by indirect immunofluorescence that the knobby feet contain a high concentration of filamentous (F-) actin, myoB (a member of Dictyostelium myosin-I family), and alpha-actinin (an actin-binding protein). Interestingly, myoB exhibits a circular disposition around each foot. Neither myosin-II (conventional myosin) nor the 269 kD protein, which has been recently identified as a talin homologue of Dictyostelium [Kreitmeier et al., 1995: J. Cell Biol. 129:179-188], are concentrated at the feet. We propose that the knobby feet provide anchorage to the substratum needed by lamellipodia to exert projectile forces for invading narrow spaces or otherwise for a flattened amoeba to secure itself to the deformable substratum. Some forms of adhesion plaques in higher organisms such as "podosomes" or "invadopodia" may perform functions similar to the knobby feet, but appear to differ in life time, cytoskeletal organization and composition. We have named the knobby foot "eupodium."
 ...
PMID:Amoeboid movement anchored by eupodia, new actin-rich knobby feet in Dictyostelium. 909 56

Left-right asymmetry is a fundamental feature of body plans, but its formation mechanisms and roles in functional lateralization remain unclear. Accumulating evidence suggests that left-right asymmetry originates in the cellular chirality. However, cell chirality has not yet been quantitatively investigated, mainly due to the absence of appropriate methods. Here we combine 3D Riesz transform-differential interference contrast (RT-DIC) microscopy and computational kinematic analysis to characterize chiral cellular morphology and motility. We reveal that filopodia of neuronal growth cones exhibit 3D left-helical motion with retraction and right-screw rotation. We next apply the methods to amoeba Dictyostelium discoideum and discover right-handed clockwise cell migration on a 2D substrate and right-screw rotation of subcellular protrusions along the radial axis in a 3D substrate. Thus, RT-DIC microscopy and the computational kinematic analysis are useful and versatile tools to reveal the mechanisms of left-right asymmetry formation and the emergence of lateralized functions.
 ...
PMID:Revealing chiral cell motility by 3D Riesz transform-differential interference contrast microscopy and computational kinematic analysis. 2925 61