Characterization of an Extensive Interface on Vitronectin for Binding to Plasminogen Activator Inhibitor-1: Adoption of Structure in an Intrinsically Disordered Region

Role of increased plasminogen activator inhibitor-1 and vitronectin in gestational diabetes mellitus

OBJECTIVE

The aim of this study was to analyze the second-trimester levels of vitronectin and plasminogen activator inhibitor-1 in gestational diabetes mellitus.

METHODS

This study was conducted between September 2020 and December 2020 at the University of Health Sciences, Bursa Yuksek Ihtisas Research and Training Hospital, Department of Obstetrics and Gynecology. A total of 30 pregnant women with gestational diabetes mellitus and 60 healthy controls between 24 and 27/6 weeks of gestation were included. The inclusion criteria were as follows: being between 18 and 45 years old and 24-27/6 gestational weeks, having singleton pregnancy, diagnosed with gestational diabetes mellitus by using a two-step challenge test. The exclusion criteria of this study were as follows: chronic inflammatory or infectious disease, fasting blood glucose>126 mg/dL, intolerance to glucose tolerance testing, abnormal liver or kidney function tests, as well as pregnancy with pre-gestational diabetes history of adverse perinatal outcomes. Serum vitronectin and plasminogen activator inhibitor-1 levels were measured using the enzyme-linked immunosorbent assay method.

RESULTS

Vitronectin and plasminogen activator inhibitor-1 levels were higher in the gestational diabetes mellitus group compared with controls [91.85 (23.08) vs. 80.10 (39.18) ng/mL, for vitronectin and 6.50 (1.05) vs. 4.35(1.0) ng/mL, for plasminogen activator inhibitor-1 (for both p<0.001)]. vitronectin >84.7 ng/mL was found to predict gestational diabetes mellitus with a sensitivity of 70% and specificity of 63.3%. Moreover, vitronectin had a significant positive correlation with fasting blood glucose (r=0.476, p<0.001), postprandial blood glucose (r=0.489, p<0.001), HbA1c (r=0.713, p<0.001), and plasminogen activator inhibitor-1 (r=0.586, p<0.001).

CONCLUSION

This study revealed that second-trimester vitronectin and plasminogen activator inhibitor-1 are increased in gestational diabetes mellitus and vitronectin could be a candidate for the prediction of gestational diabetes mellitus.

Small-angle neutron scattering contrast variation studies of biological complexes: Challenges and triumphs

Small-angle neutron scattering (SANS) has been a beneficial tool for studying the structure of biological macromolecules in solution for several decades. Continued improvements in sample preparation techniques, including deuterium labeling, neutron instrumentation and complementary techniques such as small-angle x-ray scattering (SAXS), cryo-EM, NMR and x-ray crystallography, along with the availability of more powerful structure prediction algorithms and computational resources has made SANS more important than ever as a means to obtain unique information on the structure of biological complexes in solution. In particular, the contrast variation (CV) technique, which requires a large commitment in both sample preparation and measurement time, has become more practical with the advent of these improved resources. Here, challenges and recent triumphs as well as future prospects are discussed.

Identification of a PAI-1-binding site within an intrinsically disordered region of vitronectin

The serine protease inhibitor, plasminogen activator inhibitor Type-1 (PAI-1) is a metastable protein that undergoes an unusual transition to an inactive conformation with a short half-life of only 1-2 hr. Circulating PAI-1 is bound to a cofactor vitronectin, which stabilizes PAI-1 by slowing this latency conversion. A well-characterized PAI-1-binding site on vitronectin is located within the somatomedin B (SMB) domain, corresponding to the first 44 residues of the protein. Another PAI-1 recognition site has been identified with an engineered form of vitronectin lacking the SMB domain, yet retaining PAI-1 binding capacity (Schar, Blouse, Minor, Peterson. J Biol Chem. 2008;283:28487-28496). This additional binding site is hypothesized to lie within an intrinsically disordered domain (IDD) of vitronectin. To localize the putative binding site, we constructed a truncated form of vitronectin containing 71 amino acids from the N-terminus, including the SMB domain and an additional 24 amino acids from the IDD region. This portion of the IDD is rich in acidic amino acids, which are hypothesized to be complementary to several basic residues identified within an extensive vitronectin-binding site mapped on PAI-1 (Schar, Jensen, Christensen, Blouse, Andreasen, Peterson. J Biol Chem. 2008;283:10297-10309). Steady-state and stopped-flow fluorescence measurements demonstrate that the truncated form of vitronectin exhibits the same rapid biphasic association as full-length vitronectin and that the IDD hosts the elusive second PAI-1 binding site that lies external to the SMB domain of vitronectin.