ABSTRACT
Three heterozygous mutations were identified in the genes encoding platelet integrin receptor alphaIIbbeta3 in a patient with an ill defined platelet disorder: one in the beta3 gene (S527F) and two in the alphaIIb gene (R512W and L841M). Five stable Chinese hamster ovary cell lines were constructed expressing recombinant alphaIIbbeta3 receptors bearing the individual R512W, L841M, or S527F mutation; both the R512W and L841M mutations; or all three mutations. All receptors were expressed on the cell surface, and mutations R512W and L841M had no effect on integrin function. Interestingly, the beta3 S527F mutation produced a constitutively active receptor. Indeed, both fibrinogen and the ligand-mimetic antibody PAC-1 bound to non-activated alphaIIbbeta3 receptors carrying the S527F mutation, indicating that the conformation of this receptor was altered and corresponded to the high affinity ligand binding state. In addition, the conformational change induced by S527F was evident from basal anti-ligand-induced binding site antibody binding to the receptor. A molecular model bearing this mutation was constructed based on the crystal structure of alphaIIbbeta3 and revealed that the S527F mutation, situated in the third integrin epidermal growth factor-like (I-EGF3) domain, hindered the alphaIIbbeta3 receptor from adopting a wild type-like bent conformation. Movement of I-EGF3 into a cleft in the bent conformation may be hampered both by steric hindrance between Phe(527) in beta3 and the calf-1 domain in alphaIIb and by decreased flexibility between I-EGF2 and I-EGF3.
Subject(s)
Amino Acid Substitution/genetics , Integrin beta3/genetics , Mutation/genetics , Platelet Glycoprotein GPIIb-IIIa Complex/chemistry , Platelet Glycoprotein GPIIb-IIIa Complex/genetics , Adult , Animals , Antibodies/metabolism , Binding Sites , Blood Platelet Disorders/genetics , CHO Cells , Cell Membrane/metabolism , Cricetinae , Cricetulus , Epitopes/immunology , Fibrinogen/metabolism , Humans , Integrin beta3/chemistry , Male , Mutant Proteins/metabolism , Phenylalanine/genetics , Protein Binding , Protein Conformation , Serine/geneticsABSTRACT
Gradient HPLC coupled to DAD/UV, MS/MS and NMR has been applied to the rapid structure determination of three new isomeric divanilloylquinic acids from Fagara zanthoxyloides collected in Burkina Faso: 3,4-O-divanilloylquinic acid, 3,5-O-divanilloylquinic acid and 4,5-O-divanilloylquinic acid. Furthermore these new compounds named burkinabins A-C could play a useful role in sickle cell disease, as the active agents of Fagara zanthoxyloïdes are said to be unidentified aromatic compounds with carboxylic acid grouping (Adesanya, S.A., Sofowora, A., 1983. Biological standardisation of Zanthoxylum roots for antisickling activity. Planta Med. 48, 27-33).
Subject(s)
Quinic Acid/analogs & derivatives , Vanillic Acid/analogs & derivatives , Zanthoxylum/chemistry , Anemia, Sickle Cell/metabolism , Antisickling Agents/chemistry , Antisickling Agents/isolation & purification , Antisickling Agents/pharmacology , Chromatography, High Pressure Liquid/methods , Cromolyn Sodium/pharmacology , Humans , Isomerism , Molecular Structure , Nuclear Magnetic Resonance, Biomolecular/methods , Plant Bark/chemistry , Plant Extracts/chemistry , Plant Extracts/pharmacology , Plant Roots/chemistry , Quinic Acid/chemistry , Quinic Acid/isolation & purification , Quinic Acid/pharmacology , Spectrometry, Mass, Electrospray Ionization/methods , Vanillic Acid/chemistry , Vanillic Acid/isolation & purification , Vanillic Acid/pharmacologyABSTRACT
Several studies have suggested a role of bone marrow stroma injury in long-term chemotherapy-induced hematopoietic failure. To evaluate whether bone marrow microenvironment is altered by chemotherapy for acute lymphoblastic leukemia (ALL) and to determine its contribution to postchemotherapy anemia, we investigated the ability of stroma from children receiving maintenance chemotherapy for ALL to support hematopoiesis. Long-term bone marrow cultures (LTBMC) were established with bone marrow cells either from ALL children under therapy (n = 24) or from control subjects (n = 19). Nonadherent cells and colony forming units-granulocytic monocytic (CFU-GM) output in LTBMC did not differ between patients and controls. In contrast, burst forming unit-erythroid (BFU-E) numbers were lower in patient LTBMC (p = 0.013). Co-cultures of normal CD34+ cells and preformed patient or control stromas showed significantly reduced hematopoietic supportive capabilities of patient stromas: both CFU-GM and BFU-E were reduced (p = 0.002 and 0.046, respectively). In addition, supernatants (SN) of patients' LTBMC inhibited normal BFU-E growth compared with SN of normal LTBMC. Transforming growth factor (TGF)-beta1 levels were increased in patient cultures (p = 0.0039) and inversely correlated with BFU-E produced in LTBMC (r = -0.36, p = 0.04). Neutralization of TGF-beta1 significantly increased the BFU-E output of patient LTBMC (p = 0.0078). In contrast, macrophage inflammatory peptide (MIP)-1alpha levels were lower in SN of patients compared with controls (p = 0.015). Thus, chemotherapy for ALL induces functional deregulation within bone marrow stromal cells with an increase in the growth-inhibiting factor TGF-beta1, together with a decrease in MIP-1alpha, which might contribute to hematopoietic toxicity.
