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131.
Nurizzo D Baker HM He QY MacGillivray RT Mason AB Woodworth RC Baker EN 《Biochemistry》2001,40(6):1616-1623
Human transferrin (Tf) is responsible for the binding and transport of iron in the bloodstream of vertebrates. Delivery of this bound iron to cells occurs by a process of receptor-mediated endocytosis during which Tf releases its iron at the reduced endosomal pH of approximately 5.6. Iron release from Tf involves a large conformational change in which the two domains that enclose the binding site in each lobe move apart. We have examined the role of two lysines, Lys206 and Lys296, that form a hydrogen-bonded pair close to the N-lobe binding site of human Tf and have been proposed to form a pH-sensitive trigger for iron release. We report high-resolution crystal structures for the K206A and K296A mutants of the N-lobe half-molecule of Tf, hTf/2N, and quantitative iron release data on these mutants and the double mutant K206A/K296A. The refined crystal structures (for K206A, R = 19.6% and R(free) = 23.7%; for K296A, R= 21.2% and R(free) = 29.5%) reveal a highly conserved hydrogen bonding network in the dilysine pair region that appears to be maintained even when individual hydrogen bonding groups change. The iron release data show that the mutants retain iron to a pH 1 unit lower than the pH limit of wild type hTf/2N, and release iron much more slowly as a result of the loss of the dilysine interaction. Added chloride ions are shown to accelerate iron release close to the pH at which iron is naturally lost and the closed structure becomes destabilized, and to retard it at higher pH. 相似文献
132.
As translational clinical researchers familiar with the risk-benefit of hematopoietic stem cell transplantation in autoimmune diseases, we are intrigued by the recent report of umbilical cord mesenchymal stem cell (UC-MSC) transplantation in treatment-refractory systemic lupus erythematosus nephritis by Wang and colleagues. They report the results of an open-label single-arm multicenter phase I/II study. This stimulated us to examine whether collective data from this group provide sufficient evidence for the feasibility, safety, dose rationale, and potential efficacy of UC-MSCs to conduct a randomized controlled trial in such patients. Results, though confounded by variable baseline prednisone and immuno-suppressive treatment, appear to indicate near-term response rates of approximately 50%, which are comparable to those seen with hematopoietic stem cell transplantation but with less morbidity and mortality.Wang and colleagues have been in the forefront of evaluating the potential for mesenchymal stem cells (MSCs) to treat systemic lupus erythematosus (SLE), based on studies in murine autoimmune disease models, demonstrating immunomodulatory properties of MSCs [1]. We have reviewed the additional reports published in peer-reviewed journals from this group [2–5], together with two protocols available on ClinicalTrials.gov ( and NCT00698191) (Table NCT01741857Authors (date) ClinicalTrials.gov protocol number Study design/duration of follow-up Number of patients MSC type/regimen Conditioning Safety: deaths/serious infection PD marker
a
Efficacy Sun et al. [2] NR Single-arm/ median of 8.25 months (range of 3 to 28 months) 16 (15 SLEN) UC, single infusion CYC 0.8 to 1.8 mg/kg intravenously, 2 to 4 days 0/0 Percentage of Treg cells increased at 3 months (P = 0.03) ‘Decreasing SLEDAI and proteinuriab in all patients’ Liang et al. [3] NCT 00698191 Single-arm/17.2 ± 9.5 months 15 SLEN BM, single infusion Included in protocol, but NR 0/0 Percentage of Treg cells increased at 1 week and 3 and 6 months (P <0.05) ‘Decreasing SLEDAI and proteinuriab in all patients’ Wang et al. [4] NCT 00698191 Unblinded-randomized, 2-arm/12 months 58 (~88% SLEN) BM, UC, single versus 2× (7 days apart) CYC 10 mg/kg per day, day 4, 3, and 2 1/NR ND CR single: 16/30 (53%); double: 8/27 (29%) Wang et al. [5] NR Single-arm/mean of 27 months 87 (84% SLEN) BM, UC, single infusion, 18 patients retreated at relapse CYC 10 mg/ kg/day, day 4, 3, and 2 5/NR ND CR in 23/83, relapse 10/83 Wang et al. [1]
c NCT 01741857 Single-arm 40 (38 SLEN) UC, 2× infusion, 7 days apart) No 3/4 ND MCR 13/PCR 11, 7 relapse