TNFα/IFNγ Mediated Intestinal Epithelial Barrier Dysfunction Is Attenuated by MicroRNA-93 Downregulation of PTK6 in Mouse Colonic Epithelial Cells.

Since inflammatory bowel diseases (IBD) represent significant morbidity and mortality in the US, the need for defining novel drug targets and inflammatory mechanisms would be of considerable benefit. Although protein tyrosine kinase 6 (PTK6, also known as breast tumor kinase BRK) has been primarily studied in an oncogenic context, it was noted that PTK6 null mice exhibited significantly enhanced colonic epithelial barrier function. Considering that the inflammatory functions of PTK6 have not yet been explored, we hypothesized that cytokines responsible for mediating IBD, such as TNFα/IFNγ, may solicit the action of PTK6 to alter barrier function.

Non-muscle Mlck is required for β-catenin- and FoxO1-dependent downregulation of Cldn5 in IL-1β-mediated barrier dysfunction in brain endothelial cells.

Aberrant elevation in the levels of the pro-inflammatory cytokine interleukin-1β (IL-1β) contributes to neuroinflammatory diseases. Blood-brain barrier (BBB) dysfunction is a hallmark phenotype of neuroinflammation. It is known that IL-1β directly induces BBB hyperpermeability but the mechanisms remain unclear.

Protein kinase Cα phosphorylates a novel argininosuccinate synthase site at serine 328 during calcium-dependent stimulation of endothelial nitric-oxide synthase in vascular endothelial cells.

Endothelial nitric-oxide synthase (eNOS) utilizes l-arginine as its principal substrate, converting it to l-citrulline and nitric oxide (NO). l-Citrulline is recycled to l-arginine by two enzymes, argininosuccinate synthase (AS) and argininosuccinate lyase, providing the substrate arginine for eNOS and NO production in endothelial cells. Together, these three enzymes, eNOS, AS, and argininosuccinate lyase, make up the citrulline-NO cycle.

Insulin transcriptionally regulates argininosuccinate synthase to maintain vascular endothelial function.

Diminished vascular endothelial cell nitric oxide (NO) production is a major factor in the complex pathogenesis of diabetes mellitus. In this report, we demonstrate that insulin not only maintains endothelial NO production through regulation of endothelial nitric oxide synthase (eNOS), but also via the regulation of argininosuccinate synthase (AS), which is the rate-limiting step of the citrulline-NO cycle. Using serum starved, cultured vascular endothelial cells, we show that insulin up-regulates AS and eNOS transcription to support NO production.

Argininosuccinate synthase: at the center of arginine metabolism.

The levels of L-arginine, a cationic, semi-essential amino acid, are often controlled within a cell at the level of local availability through biosynthesis. The importance of this temporal and spatial control of cellular L-arginine is highlighted by the tissue specific roles of argininosuccinate synthase (argininosuccinate synthetase) (EC 6.3.