SP-40,40 is a component of plasminogen activator inhibitor-1-binding protein and stabilizes plasminogen activator inhibitor-1 activity

The comparative analysis of serum proteomes for the discovery of biomarkers for acute myeloid leukemia

OBJECTIVE

Acute myeloid leukemia (AML) develops as the consequence of a series of genetic changes in a hematopoietic precursor cell. However, the definitive diagnostic protein biomarkers for AML are still unclear. In our study to identify the biomarkers for an initial diagnosis, detection of relapse, and monitoring the minimal residual disease in AML by a less invasive method, serum proteins reflecting alterations in their proteomes were analyzed.

MATERIALS AND METHODS

We compared the two-dimensional electrophoresis patterns of human sera of 12 patients with AML with those of 12 normal subjects. The differentially expressed spots were identified by matrix-assisted laser desorption/ionization time-of-flight and electrospray ionization quadupole time-of-flight mass spectrometries.

RESULTS

Eight proteins that expressed differentially in the AML group were found. The expression levels of alpha-2-HS-glycoprotein, complement-associated protein SP-40, 40, RBP4 gene product, lipoprotein C-III, and an unknown protein were downregulated in serum of AML patients, whereas the other three proteins, including immunoglobulin heavy-chain variant, proteosome 26S ATPase subunit 1, and haptoglobin-1 were upregulated.

CONCLUSION

These results suggest that these proteins can be used as less invasive diagnostic and monitoring biomarkers of AML if further studies are done.

Plasminogen activator inhibitor-1 and the kidney

Plasminogen activator inhibitor-1 (PAI-1) is a serine protease inhibitor that was isolated 20 years ago. First recognized as an inhibitor of intravascular fibrinolysis, it is now evident that PAI-1 is a multifunctional protein with actions that may be dependent on or independent of its protease inhibitory effects. The latter often involve interactions between PAI-1 and vitronectin or the urokinase receptor. The protease-inhibitory actions of PAI-1 extend beyond fibrinolysis and include extracellular matrix turnover and activation of several proenzymes and latent growth factors. PAI-1 has been implicated in several renal pathogenetic processes, including thrombotic microangiopathies and proliferative and/or crescentic glomerulopathies. Most recently, it has become clear that PAI-1 also plays a pivotal role in progressive renal disease, both glomerulosclerosis and tubulointerstitial fibrosis. An active area of present research interest, untold stories are likely to be uncovered soon.

Enhanced expression of plasminogen activator inhibitor-1 by dedifferentiated thyrocytes

Porcine thyrocytes in vitro in the presence of TSH adopt follicular-like morphology. Epidermal growth factor, phorbol esters or transforming growth factor beta-1 (TGFbeta-1) induce a rapid spreading of the cells and dedifferentiation. In addition to thyroglobulin, dedifferentiated thyrocytes secreted into the culture medium three proteins in abundant quantities. Two of them have been previously identified as thrombospondin-1 and clusterin, respectively. Using the microsequencing method we identified the third one, a M(r) 45,000 glycosylated protein, as plasminogen activator inhibitor-1 (PAI-1). EGF, phorbol esters or TGF-beta1 predominantly increased PAI-1 protein expression in TSH-treated cells. The maximal increase of PAI-1 mRNA steady-state level was observed 6 h after EGF treatment and sustained up to 48 h. Recombinant PAI-1 inhibited cell-associated plasmin activity and delayed cell spreading. Enhanced synthesis and secretion of PAI-1 upon treatment with different growth factors during dedifferentiation process and spreading may be considered a feed-back defence mechanism of the cells to harmful extracellular stimuli.