Role of sulfhydryl groups in band 3 in the inhibition of phosphate transport across erythrocyte membrane in visceral leishmaniasis

2005 ◽  
Vol 436 (1) ◽  
pp. 121-127 ◽  
Author(s):  
Sudipa Saha Roy ◽  
Gargi Sen ◽  
Tuli Biswas
Keyword(s):  
Visceral Leishmaniasis ◽  
Erythrocyte Membrane ◽  
Phosphate Transport ◽  
Band 3 ◽  
Sulfhydryl Groups

scholarly journals Eryptotic Phenotype in Chronic Myeloid Leukemia: Contribution of Neutrophilic Cathepsin G

Anemia ◽  
2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
Rukmini Govekar ◽  
Poonam Kawle ◽  
Renjan Thomas ◽  
Suresh Advani ◽  
Sheena PV ◽  
...  
Keyword(s):  
Chronic Myeloid Leukemia ◽  
Erythrocyte Membrane ◽  
Myeloid Leukemia ◽  
Band 3 ◽  
Cathepsin G ◽  
Myeloproliferative Disease ◽  
Pathological Conditions ◽  
First Time ◽  
Erythrocyte Membrane Proteins

In pathological conditions with concurrent neutrophilia, modifications of erythrocyte membrane proteins are reported. In chronic myeloid leukemia (CML), a myeloproliferative disease wherein neutrophilia is accompanied by enhanced erythrophagocytosis, we report for the first time excessive cleavage of erythrocyte band 3. Distinct fragments of band 3 serve as senescent cell antigens leading to erythrophagocytosis. Using immunoproteomics, we report the identification of immunogenic 43 kDa fragment of band 3 in 68% of CML samples compared to their detection in only 38% of healthy individuals. Thus, excessive fragmentation of band 3 in CML, detected in our study, corroborated with the eryptotic phenotype. We demonstrate the role of neutrophilic cathepsin G, detected as an immunogen on erythrocyte membrane, in band 3 cleavage. Cathepsin G from serum adsorbs to the erythrocyte membrane to mediate cleavage of band 3 and therefore contribute to the eryptotic phenotype in CML.

Role of Mechanical Stress on the Transglutaminase -Mediated Crosslinking of Erythrocyte Membrane Proteins.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 1588-1588
Author(s):  
Edgar Gutierrez ◽  
Lanping Amy Sung
Keyword(s):  
Membrane Proteins ◽  
Mechanical Stress ◽  
Erythrocyte Membrane ◽  
Calcium Influx ◽  
Mechanical Deformation ◽  
Band 3 ◽  
Ionophore A23187 ◽  
Acyl Acceptor ◽  
Erythrocyte Membrane Proteins

Abstract The life-span of erythrocytes is relatively constant within species and it may be determine by the number of times the cell passes through the circulatory system — enduring repeated cycles of mechanical stress. The intrinsic transglutaminase is the major enzyme capable of catalyzing covalent γ-glutamyl-ε-lysine crosslinks that enhance erythrocyte membrane rigidity. Here we report the cloning of mouse erythrocyte transglutaminase (TG) and the role of mechanical stress on the TG-mediated crosslinking of erythrocyte membrane proteins. TG was PCR cloned from reticulocyte cDNA by using consensus primers. Northern blot analysis of the polyA+ mRNA revealed the TG transcript to be 4.6 kb. Recombinant TG was expressed in yeast and the enzymatic crosslinking was detected by labeling glutamine (Q) acyl-donors in inside out vesicles (IOVs) with fluorescent dansylcadaverine (DNC), which serves as the acyl-acceptor. Crosslinking of spectrin/ankyrin, protein 4.1, and band 3 regions (known Q-donors) by TG required CaCl2 at 0.1–0.25 mM and was regulated by both GTP (optimal at 0.01–0.05 mM) and ATP (optimal at 0.5–2.0 mM) with inhibitory effects at higher concentrations. Protein 4.2 (P4.2), a TG pseudo-enzyme, and the cytoplasmic domain of band 3 (cdb3) were also produced recombinantly which allowed for an in-vitro model to test molecular interactions with TG. Specifically, the crosslinking of cdb3 by TG and the binding of P4.2 and TG to cdb3 were examined. A rise in [CaCl2] to near 1 mM showed increased activity of TG (~75% of maximal activity) together with a slight decrease in TG binding affinity to cdb3 (~25% decrease). The crosslinking of cdb3 by TG was inhibited by P4.2, however the presence of P4.2 facilitated the binding of TG to cdb3. The analysis of endogenous TG activity in intact erythrocytes subjected to mechanical stress by hypo-osmolarity (equi-biaxial stretch) or shear stress (anisotropic extension) was also performed. Hypo-osmotically stressed DNC-loaded erythrocytes in the presence of 2 mM [CaCl2] produced a profile with a less intense crosslinking as compared to that of IOVs. In addition, two novel Q-donors (Q1 and Q2) that required mechanical deformation of the membrane to be crosslinked were discovered. Mechanical shearing of erythrocytes in a viscometer produced a similar profile, again with Q2 being the most crosslinked Q-donor. The ratio of Q2/band 3 crosslinking under shear, however, was two fold greater than that under hypo-osmotically induced stress, indicating that varying degrees of crosslinking may be induced by different modes of mechanical stress. Interestingly, Q2 also became crosslinked in IOVs prepared from erythrocytes previously hyposmotically incubated in the presence of extracellular calcium. The importance of mechanical deformation and calcium influx in the binding of Q2 to membrane-associated proteins was further supported by the findings that calcium introduced into erythrocytes using ionophore A23187 alone was not sufficient to induce the crosslinking of Q2. Together these experiments support our hypothesis that periodic mechanical stress may serve as an inherent molecular timer. It is likely that the activation of TG by transient increases in near-membrane calcium concentrations may lead to the accumulation of crosslinks of proteins at the membrane and an eventual entrapment of less deformable erythrocytes in the sinusoids in the spleen followed by subsequent phagocytosis through the recognition of band 3 auto-antibodies.

Sign in / Sign up

Export Citation Format

Share Document