Expression of Cholesterol Sulfotransferase (SULT2B1b) in Human Platelets

Abstract

Background-Cholesterol sulfate, the most important sterol sulfate in the human circulation, has emerged as a multifaceted molecule. Among its many demonstrated regulatory actions is its ability to influence blood clotting and fibrinolysis. Additionally, cholesterol sulfate is a constituent of human platelets, where it has been shown to support platelet aggregation. Methods and Results-We have documented the presence of the enzyme (SULT2B1b) that sulfonates cholesterol in human platelets and examined the influence of plasma lipoproteins on the expression and activity of this enzyme. SULT2B1b mRNA was detected by reverse transcription-polymerase chain reaction and found to be the only steroid/sterol sulfotransferase expressed in these discoid anucleate particles. Using real-time polymerase chain reaction for quantification, we found that the level of SULT2B1b mRNA in platelets was maintained at 4°C but substantially diminished over a period of 4 hours at 37°C. The loss of SULT2B1b mRNA, however, was markedly reduced in the presence of HDL but not LDL. The stabilizing influence of HDL was attributable specifically to its apolipoprotein (apo) A-I component, whereas apoA-II and apoE were without effect. Importantly, there was a direct correlation between platelet SULT2B1b mRNA and protein levels in the presence or absence of lipoprotein that was reflected in enzymatic activity and cholesterol sulfate production. Conclusions-Human platelets selectively express SULT2B1b, the physiological cholesterol sulfotransferase. Furthermore, the stability of SULT2B1b mRNA and protein in platelets maintained at 37°C is subject to regulation by the apoA-I component of HDL.

Is Endothelial Nitric Oxide Synthase a Moonlighting Protein Whose Day Job is Cholesterol Sulfate Synthesis? Implications for Cholesterol Transport, Diabetes and Cardiovascular Disease

“…RBCs export ATP to support the conversion of sulfate to PAPS. Platelets perform the final step of producing Ch-S within the extracellular matrix of the atheroma [99]. Inflammation has long been recognized as a critical factor in cardiovascular disease [206], and our view is that a key inflammatory agent, superoxide, is needed as substrate to produce sulfate from homocysteine thiolactone [104].…”

“…Like RBCs, platelets also inexplicably contain a functional eNOS [5], and they also produce Ch-S [99]. Platelets produce an abundance of Ch-S from cholesterol in the presence of PAPS.…”

“…A quote from [99] captures the level of surprise that the researchers experienced in their experiments on platelets: "The remarkable increase in platelet cholesterol sulfate content (300-fold) after the addition of exogenous PAPS to the incubation medium was totally unexpected." [99] Chronically inflamed tissues support high levels of lymphocyte extravasation from the blood, and the initial adhesion of these immune cells to the vessel wall is mediated by selectins [100], whose ligands are sulfated sialomucins. In [101], it was demonstrated that endothelial cells in inflamed tissues possess active expression of the gene for ATP sulfurylase, which catalyzes the synthesis of PAPS from sulfate.…”

“…In [99], it was demonstrated that platelets will only accept cholesterol from HDL-A1 as a source for Ch-S synthesis-they reject not only all forms of LDL, but also other apolipoproteins bound to HDL such as apoE and apoA-II.…”

Cytosolic sulfotransferase 2B1b promotes hepatocyte proliferation gene expression in vivo and in vitro

“…The SULT2 family contains two subfamilies, SULT2A1 and SULT2B1, and the SULT2B1 subfamily is additionally divided into two isoforms, SULT2B1a and SULT2B1b (23). SULT2B1b expresses in multiple human tissues, including placenta, prostate, breast, skin, lung, small intestine, liver, and platelets (15,21,22,24,31,35,49). SULT2B1b effectively catalyzes the sulfation of 3␤-hydroxysteroids and functions as a selective cholesterol and oxysterol sulfotransferase (1,12,16,17,31,36).…”