The localization of α-synuclein in the process of differentiation of human erythroid cells.

Although the neuronal protein α-synuclein (α-syn) is thought to play a central role in the pathogenesis of Parkinson's disease (PD), its physiological function remains unknown. It is known that α-syn is also abundantly expressed in erythrocytes. However, its role in erythrocytes is also unknown.

Conserved and unique thermodynamic properties of lactate dehydrogenases in an ectothermic organism, the teleost Microstomus achne, and an endothermic organism, bovine.

It is widely believed that enzymatic activities in ectothermic organisms adapt to environmental temperatures. However, to date, no study has thoroughly compared multiple thermodynamic enzymatic characteristics across species living in dramatically different environments. To start to address this gap, we compared the characteristics of lactate dehydrogenase (LDH) purified from the muscles from slime flounder Microstomus achne white muscle and bovine skeletal muscle (bM) and heart.

Enzymatic and thermodynamic profiles of a heterotetramer lactate dehydrogenase isozyme in swine.

Lactate dehydrogenase (LDH) is a glycolytic enzyme that catalyzes the final step of glycolysis and produces NAD. In somatic cells, LDH forms homotetramers and heterotetramers that are encoded by two different genes: LDHA (skeletal muscle type, M) and LDHB (heart type, H). Analysis of LDH isozymes is important for understanding the physiological role of homotetramers and heterotetramers and for optimizing inhibition of their enzymatic activity as it may result in distinct effects.

[Phylogenic insights into the enucleation of erythroblasts in human].

Two key questions remain unanswered in the erythropoiesis field: Why and how do erythroblasts enucleate in mammalian species? Recent studies have unveiled the roles of various molecules, cytoskeletal proteins, motor proteins, vesicle transport, signaling pathways, lipid rafts and actomyosin ring contraction in the enucleation process. However, few reports provide insights into the fitness benefit for mammalian species of having anucleate erythrocytes. Herein, we discuss the biological significance of enucleation of human erythroblasts based on our recent results and on evolutionary considerations related to the biology of hemoglobin and the comparative biochemistry of erythrocyte membrane cytoskeletal proteins, such as protein 4.

Hydroxychloroquine binding to cytoplasmic domain of Band 3 in human erythrocytes: Novel mechanistic insights into drug structure, efficacy and toxicity.

Hydroxychloroquine (HCQ) is a widely used drug in the treatment of autoimmune diseases, such as arthritis and systemic lupus erythematosus. It has also been prescribed for the treatment of malaria owing to its lower toxicity compared to its closely related compound chloroquine (CQ). However, the mechanisms of action of HCQ in erythrocytes (which bind preferentially this drug) have not been documented and the reasons underlying the lower side effects of HCQ compared to CQ remain unclear.

Erythroblast enucleation is a dynein-dependent process.

Mammalian erythroblasts undergo enucleation through a process thought to be similar to cytokinesis. Microtubule-organizing centers (MTOCs) mediate organization of the mitotic spindle apparatus that separates the chromosomes during mitosis and are known to be crucial for proper cytokinesis. However, the role of MTOCs in erythroblast enucleation remains unknown.

Phosphatidylinositol-4,5 bisphosphate (PIP(2)) inhibits apo-calmodulin binding to protein 4.1.

Membrane skeletal protein 4.1R(80) plays a key role in regulation of erythrocyte plasticity. Protein 4.

Unique structural changes in calcium-bound calmodulin upon interaction with protein 4.1R FERM domain: novel insights into the calcium-dependent regulation of 4.1R FERM domain binding to membrane proteins by calmodulin.

Calmodulin (CaM) binds to the FERM domain of 80 kDa erythrocyte protein 4.1R (R30) independently of Ca(2+) but, paradoxically, regulates R30 binding to transmembrane proteins in a Ca(2+)-dependent manner. We have previously mapped a Ca(2+)-independent CaM-binding site, pep11 (A(264)KKLWKVCVEHHTFFR), in 4.

Zinc-L-carnosine binds to molecular chaperone HSP70 and inhibits the chaperone activity of the protein.

In this study, we have investigated the specific binding proteins of Zinc-L-carnosine (Polaprezinc) using Polaprezinc-affinity column chromatography in vitro. A protein having a 70-kDa molecular mass was eluted by the linear gradient of 0-1.0 mM Polaprezinc from the affinity column and the protein was identified as the molecular chaperone HSP70 by immunoblotting.

Novel mechanism of regulation of protein 4.1G binding properties through Ca2+/calmodulin-mediated structural changes.

Protein 4.1G (4.1G) is a widely expressed member of the protein 4.

Characterization of cytoskeletal protein 4.1R interaction with NHE1 (Na(+)/H(+) exchanger isoform 1).

NHE1 (Na(+)/H(+) exchanger isoform 1) has been reported to be hyperactive in 4.1R-null erythrocytes [Rivera, De Franceschi, Peters, Gascard, Mohandas and Brugnara (2006) Am. J.

Light scattering: a novel approach to analyze protein 4.1R FERM domain interaction with inside-out-vesicles in solution.

In this study, we describe a novel application for light scattering, a method widely used for separation of molecules in solution based on their size. We demonstrate that light scattering analysis can monitor the change in particle size of protein 4.1R prior to and after binding to red blood cell inside-out-vesicles in solution.

Dynamic secondary structural changes in Ca²⁺-saturated calmodulin upon interaction with the antagonist, W-7.

Although the 3D structure of the Ca(2+)-bound CaM (Ca(2+)/CaM) complex with the antagonist, N-(6-aminohexyl)-5-chloro-1-naphthalenesulphonamide (W-7), has been resolved, the dynamic changes in Ca(2+)/CaM structure upon interaction with W-7 are still unknown. We investigated time- and temperature-dependent dynamic changes in Ca(2+)/CaM interaction with W-7 in physiological conditions using one- and two-dimensional Fourier-transformed infrared spectroscopy (2D-IR). We observed changes in the α-helix secondary structure of Ca(2+)/CaM when complexed with W-7 at a molar ratio of 1:2, but not at higher molar ratios (between 1:2 and 1:5).

Enucleation of human erythroblasts involves non-muscle myosin IIB.

Mammalian erythroblasts undergo enucleation, a process thought to be similar to cytokinesis. Although an assemblage of actin, non-muscle myosin II, and several other proteins is crucial for proper cytokinesis, the role of non-muscle myosin II in enucleation remains unclear. In this study, we investigated the effect of various cell-division inhibitors on cytokinesis and enucleation.

Insights into the Function of the Unstructured N-Terminal Domain of Proteins 4.1R and 4.1G in Erythropoiesis.

Membrane skeletal protein 4.1R is the prototypical member of a family of four highly paralogous proteins that include 4.1G, 4.

Structural stabilization of protein 4.1R FERM domain upon binding to apo-calmodulin: novel insights into the biological significance of the calcium-independent binding of calmodulin to protein 4.1R.

In erythrocytes, 4.1R80 (80 kDa isoform of protein 4.1R) binds to the cytoplasmic tail of the transmembrane proteins band 3 and GPC (glycophorin C), and to the membrane-associated protein p55 through the N- (N-terminal), α- (α-helix-rich) and C- (C-terminal) lobes of R30 [N-terminal 30 kDa FERM (4.

Two different unique cardiac isoforms of protein 4.1R in zebrafish, Danio rerio, and insights into their cardiac functions as related to their unique structures.

Protein 4.1R (4.1R) has been identified as the major component of the human erythrocyte membrane skeleton.

Similarities and differences in the structure and function of 4.1G and 4.1R135, two protein 4.1 paralogues expressed in erythroid cells.

Membrane skeletal protein 4.1R is the prototypical member of a family of four highly paralogous proteins that include 4.1G, 4.

High affinity of interaction between superantigen and T cell receptor Vbeta molecules induces a high level and prolonged expansion of superantigen-reactive CD4+ T cells.

In mice implanted with an osmotic pump filled with the superantigen (SAG) staphylococcal enterotoxin A (SEA), the Vβ3(+)CD4(+) T cells exhibited a high level of expansion whereas the Vβ11(+)CD4(+) T cells exhibited a mild level of expansion. In contrast, in mice implanted with an osmotic pump filled with SE-like type P (SElP, 78.1% homologous with SEA), the Vβ11(+)CD4(+) T cells exhibited a high level of expansion while the Vβ3(+)CD4(+) T cells exhibited a low level of expansion, suggesting that the level of the SAG-induced response is determined by the affinities between the TCR Vβ molecules and SAG.

Dynamics of human erythroblast enucleation.

How human erythroblasts enucleate remains obscure, and some investigators suspect the effect of mechanical forces on enucleation in vitro. We determined the dynamics of the enucleation process of highly purified human erythroblasts and whether enucleation can occur without external mechanical forces. Highly purified human CD34(+) cells were cultured in liquid phase with interleukin-3, stem cell factor and erythropoietin (EPO) for 7 days and the generated erythroblasts were replaced in the same medium with EPO alone.

Marked difference in membrane-protein-binding properties of the two isoforms of protein 4.1R expressed at early and late stages of erythroid differentiation.

Two major isoforms of protein 4.1R, a 135 kDa isoform (4.1R(135)) and an 80 kDa isoform (4.

Interactions of Plasmodium falciparum erythrocyte membrane protein 3 with the red blood cell membrane skeleton.

Plasmodium falciparum parasites express and traffick numerous proteins into the red blood cell (RBC), where some associate specifically with the membrane skeleton. Importantly, these interactions underlie the major alterations to the modified structural and functional properties of the parasite-infected RBC. P.