Decreased phenol sulfotransferase activities associated with hyperserotonemia in autism spectrum disorders

Hyperserotonemia is the most replicated biochemical abnormality associated with autism spectrum disorders (ASD). However, previous studies of serotonin synthesis, catabolism, and transport have not elucidated the mechanisms underlying this hyperserotonemia. Here we investigated serotonin sulfation by phenol sulfotransferases (PST) in blood samples from 97 individuals with ASD and their first-degree relatives (138 parents and 56 siblings), compared with 106 controls. We report a deficient activity of both PST isoforms (M and P) in platelets from individuals with ASD (35% and 78% of patients, respectively), confirmed in autoptic tissues (9 pineal gland samples from individuals with ASD—an important source of serotonin). Platelet PST-M deficiency was strongly associated with hyperserotonemia in individuals with ASD. We then explore genetic or pharmacologic modulation of PST activities in mice: variations of PST activities were associated with marked variations of blood serotonin, demonstrating the influence of the sulfation pathway on serotonemia. We also conducted in 1645 individuals an extensive study of SULT1A genes, encoding PST and mapping at highly polymorphic 16p11.2 locus, which did not reveal an association between copy number or single nucleotide variations and PST activity, blood serotonin or the risk of ASD. In contrast, our broader assessment of sulfation metabolism in ASD showed impairments of other sulfation-related markers, including inorganic sulfate, heparan-sulfate, and heparin sulfate-sulfotransferase. Our study proposes for the first time a compelling mechanism for hyperserotonemia, in a context of global impairment of sulfation metabolism in ASD.

An activity-based fluorescent sensor for the detection of the phenol sulfotransferase SULT1A1 in living cells

Here, we report the development, computational modeling, in vitro enzymology, and biological application of an activity-based fluorescent sensor for the human phenol sulfotransferase SULT1A1.

An Activity-Based Fluorescent Sensor for the Detection of the Phenol Sulfotransferase SULT1A1 in Living Cells

<p>The biological activation and incorporation of inorganic sulfate proceeds via a process known as sulfurylation. Transfer of a sulfuryl moiety from the activated sulfate donor, 3’-phosphoadenosine-5’-phosphosulfate (PAPS), to hydroxy-containing substrates by human phenol sulfotransferases (SULT1 family) alters substrate solubility and charge to affect the metabolism of endogenous metabolites, xenobiotics, and drugs. Current methods to monitor SULT1 activity in living cells primarily rely on radiolabeling and/or cell extractions, but these methods do not provide a direct readout of enzyme activity with a dynamic, temporally resolved spatial map in live, intact cells. To fill this gap, here, we present the development, computational modeling, <i>in vitro</i> enzymology, and biological application of Sulfotransferase Sensor-3, STS-3, an activity-based fluorescent sensor for SULT1A1, the most widely expressed and promiscuous SULT1 isoform. </p>

An Activity-Based Fluorescent Sensor for the Detection of the Phenol Sulfotransferase SULT1A1 in Living Cells

<p>The biological activation and incorporation of inorganic sulfate proceeds via a process known as sulfurylation. Transfer of a sulfuryl moiety from the activated sulfate donor, 3’-phosphoadenosine-5’-phosphosulfate (PAPS), to hydroxy-containing substrates by human phenol sulfotransferases (SULT1 family) alters substrate solubility and charge to affect the metabolism of endogenous metabolites, xenobiotics, and drugs. Current methods to monitor SULT1 activity in living cells primarily rely on radiolabeling and/or cell extractions, but these methods do not provide a direct readout of enzyme activity with a dynamic, temporally resolved spatial map in live, intact cells. To fill this gap, here, we present the development, computational modeling, <i>in vitro</i> enzymology, and biological application of Sulfotransferase Sensor-3, STS-3, an activity-based fluorescent sensor for SULT1A1, the most widely expressed and promiscuous SULT1 isoform. </p>

Dose- and time-dependent glucocorticoid receptor signaling in podocytes

Glucocorticoids (GC) are the primary therapy for idiopathic nephrotic syndrome (NS). Recent evidence has identified glomerular podocytes as a potential site of GC action in this disease. The objectives of this study were to determine the presence of key components of the glucocorticoid receptor (GR) complex and the functionality of this signaling pathway in podocytes and to explore potential opportunities for manipulation of GC responsiveness. Here, we show that cultured murine podocytes express key components of the GR complex, including the GR, heat shock protein 90, and the immunophilins FKBP51 and FKBP52. The functionality of GR-mediated signaling was verified by measuring several GC (dexamethasone)-induced responses, including 1) increases in mRNA and protein levels of selected GC-regulated genes (FKBP51, phenol sulfotransferase 1, αB-crystallin); 2) downregulation of the GR protein; 3) increased phosphorylation of the GR; and 4) translocation of the GR into the nuclear fraction. Dexamethasone-induced phosphorylation and downregulation of GR protein were also demonstrated in isolated rat glomeruli. Podocyte gene expression in response to dexamethasone was regulated at both the transcriptional and posttranscriptional levels, the latter also including protein degradation. Short-term, high-dose GC treatment resulted in similar changes in gene expression and GR phosphorylation to that of long-term, low-dose GC treatment, thus providing a molecular rationale for the known efficacy of pulse GC therapy in NS. Induction of FKBP51 and downregulation of the GR represent negative feedback mechanisms that can potentially be exploited to improve clinical GC efficacy. Collectively, these findings demonstrate the presence of key molecular components of the GR signaling pathway and its functionality in podocytes and identify novel opportunities for improving clinical GC efficacy in the treatment of NS.