Understanding Conformational Regulation of the Integrin I-domain for Design of Chimeric Protein Switches

Within all complex biological processes intricate proteins are expressed to complete every niche and necessary task. Many express multiple allosterically regulated conformational states, with protein function regulated by effector molecules and other ligands. One such protein is the LFA-1 surface integrin protein and its inserted domain, the I-domain. We Isolated the I-domain for investigation of determining binding properties and understanding conformational regulations of affinity changes to its target ligand ICAM-1, for further use in chimeric protein switch design. A large change in binding affinity was found through the deletion of a sub-sequence of amino acids in I-domain known as the α7 helix. Our investigation shows that, when the α7 helix is deleted, I-domain converts into a permanent high affinity state in which binding affinity to ICAM-1 was increased, and this state can be reversed by co-expression with soluble α7 helix peptide. These results conclude that the α7 helix stabilizes the I domain in its low affinity conformation in a ligand-like manner, allowing relaxation to the high affinity conformation upon disruption of α7 helix interaction. While deletion of the α7 helix yields higher binding affinity in I-domain it cannot be applied in design of chimeric protein switches due to its permanent conformational state. Because of this, our switch design has a focus of allosterically regulating the I-domain and α7 helix through utilizing on/off switching of conformational states. I-domain is fused with EF3 and EF4 hands of calmodulin, which then regulates binding affinity to ICAM-1 through interaction with α7 helix, when the EF hands’ natural ligand peptides are present. Currently, mutant switches are being developed to alter EF hand binding specificity which, when bound to new target ligands, will cause an increase in I-domain-ICAM-1 binding affinity in switch molecules. The results of these allosteric regulations highlight the potential of chimeric protein switches for design of environmentally responsive targeting agents and suggest that, through directed evolution, regulated binding to a range of novel targets could be achieved for therapeutic intervention

Empagliflozin in Patients with Chronic Kidney Disease

Background The effects of empagliflozin in patients with chronic kidney disease who are at risk for disease progression are not well understood. The EMPA-KIDNEY trial was designed to assess the effects of treatment with empagliflozin in a broad range of such patients. Methods We enrolled patients with chronic kidney disease who had an estimated glomerular filtration rate (eGFR) of at least 20 but less than 45 ml per minute per 1.73 m(2) of body-surface area, or who had an eGFR of at least 45 but less than 90 ml per minute per 1.73 m(2) with a urinary albumin-to-creatinine ratio (with albumin measured in milligrams and creatinine measured in grams) of at least 200. Patients were randomly assigned to receive empagliflozin (10 mg once daily) or matching placebo. The primary outcome was a composite of progression of kidney disease (defined as end-stage kidney disease, a sustained decrease in eGFR to < 10 ml per minute per 1.73 m(2), a sustained decrease in eGFR of & GE;40% from baseline, or death from renal causes) or death from cardiovascular causes. Results A total of 6609 patients underwent randomization. During a median of 2.0 years of follow-up, progression of kidney disease or death from cardiovascular causes occurred in 432 of 3304 patients (13.1%) in the empagliflozin group and in 558 of 3305 patients (16.9%) in the placebo group (hazard ratio, 0.72; 95% confidence interval [CI], 0.64 to 0.82; P < 0.001). Results were consistent among patients with or without diabetes and across subgroups defined according to eGFR ranges. The rate of hospitalization from any cause was lower in the empagliflozin group than in the placebo group (hazard ratio, 0.86; 95% CI, 0.78 to 0.95; P=0.003), but there were no significant between-group differences with respect to the composite outcome of hospitalization for heart failure or death from cardiovascular causes (which occurred in 4.0% in the empagliflozin group and 4.6% in the placebo group) or death from any cause (in 4.5% and 5.1%, respectively). The rates of serious adverse events were similar in the two groups. Conclusions Among a wide range of patients with chronic kidney disease who were at risk for disease progression, empagliflozin therapy led to a lower risk of progression of kidney disease or death from cardiovascular causes than placebo