CAT2-mediated l-arginine transport and nitric oxide production in activated macrophages

Abstract

Activated macrophages require l-arginine uptake to sustain NO synthesis. Several transport systems could mediate this l-arginine influx. Using competition analysis and gene-expression studies, amino acid transport system y+ was identified as the major carrier responsible for this activity. To identify which of the four known y+ transport-system genes is involved in macrophage-induced l-arginine uptake, we used a hybrid-depletion study in Xenopus oocytes. Cationic amino acid transporter (CAT) 2 antisense oligodeoxyribonucleotides abolished the activated-macrophage-mRNA-induced l-arginine transport. Together with expression studies documenting that CAT2 mRNA and protein levels are elevated with increased l-arginine uptake, our data demonstrate that CAT2 mediates the l-arginine transport that is required for the raised NO production in activated J774 macrophages.

Signal integration between IFNγ and TLR signalling pathways in macrophages

“…NF-kB) transcription factors at the Inos promoter, as well as other mechanisms by which IFNg primes macrophage nitric oxide production (e.g. induction of argininosuccinate synthetase and GTP-cyclohydroxylase I, (reviewed in Schroder et al, 2004), and coordinate upregulation of the CAT2 arginine transporter (Kakuda et al, 1999)). LPS is able to provide both signals at the Inos promoter (as NF-kB is the canonical TLR-induced transcription factor, and autocrine type I IFN activates STAT1).…”

Renal transcription of high‐affinity type‐2 cationic amino acid transporter is up‐regulated in LPS‐stimulated rodents

“…Using a cultured astraglial cell model, Stevens et al further demonstrated that induced NO biosynthesis depends on induced alternatively spliced transcript of highaffinity CAT-2, a single 123-base nucleotide sequence coding the high-affinity domain of transport system y þ (15). In a later study using a model of stimulated macrophages to form iNOS, Kakuda et al showed that bacterial toxins also up-regulate high-affinity CAT-2 (20). Using a lipopolysaccharide (LPS)-stimulated murine macrophages cell-culture model, we found that interleukin (IL)-10 inhibition of NO biosynthesis involves suppression of high-affinity CAT-2 transcription (21).…”

Increased cationic amino acid flux through a newly expressed transporter in cells overproducing nitric oxide from patients with septic shock

“…This is due predominantly to an increase in y + transporter activity, consistent with the observed increase in the mRNA encoding CAT2, a y + transporter protein. The molecular basis of similar changes in animal models is most consistently an increase in CAT2 mRNA [10,23,28,29], although many animal models also show a simultaneous increase in CAT1 [30][31][32][33]. In that CAT1 mRNA levels were not changed in clinical human sepsis, the present study highlights the limitations of these animal models of human disease.…”