Disease relevance of SLC7A3

• In Xenopus laevis oocytes and human U373MG glioblastoma cells, hCAT-3-mediated L-arginine transport was significantly reduced upon treatment with compounds that activate classical PKC [1].
• On the other hand, the Cat3 transcript is up-regulated by dehydration and osmotic stress only in ABA-deficient mutant leaves, implying that ABA may act as a repressor for Cat3 expression in response to dehydration and high osmoticum [2].

High impact information on SLC7A3

• In the CAT family, three genes encode for four different isoforms [CAT-1, CAT-2A, CAT-2(B) and CAT-3]; these are approximately 70-kDa proteins with multiple transmembrane segments (12-14), and despite their structural similarity, they differ in tissue distribution, kinetics, and regulatory properties [3].
• This circadian rhythm in Cat3 gene expression and the resulting high levels of mRNA which accumulate late in the light period suggest that the catalase 3 (CAT-3) isozyme is being synthesized for accumulation in the dark period [4].
• This, together with the high level of Cat3 mRNA and CAT-3 protein accumulation in dark-grown maize shoots, suggests that the activity of the CAT-3 isozyme might be associated with a metabolic process important in shoot cells in the dark [4].
• In oocyte injection assays, CAT3 cRNA exhibited a saturable, sodium ion-independent transport activity with high affinity for L-arginine and L-lysine (Km = 40-60 and 115-165 microM, respectively) [5].
• The presence of L-arginine in the incubation medium stimulated the efflux rate of L-arginine, indicating that CAT3 is subject to trans-stimulation [5].

Biological context of SLC7A3

• Oocytes expressing hCAT-3 displayed less negative membrane potentials and larger voltage-dependent currents than native or water-injected oocytes did [6].
• The Cat3 gene of maize exhibits a transcriptionally regulated circadian rhythm [7].
• The results suggest that the molecular basis for Cat3 null phenotype in IDS28 may be a deletion in the 5' end of the Cat3 gene [8].
• Two of the Cat2 introns are located in the same position as the two Cat3 introns [9].

Anatomical context of SLC7A3

• Transport studies in Xenopus laevis oocytes revealed that hCAT-3 is selective for cationic L-amino acids and exhibits a maximal transport activity similar to other CAT proteins [10].
• We have cloned a cDNA containing the complete coding region of human CAT-3. hCAT-3 is glycosylated and localized to the plasma membrane [10].
• Human CAT-3 expression is not restricted to the brain, in fact, by far the highest expression was found in thymus [10].
• In contrast to its highly localized expression during the primitive streak stage and in the adult stage, CAT3 expression was detected more widely in 13.5 day post-coitum mouse embryos [5].
• The induction of the Cat3 circadian expression in etiolated leaves is probably regulated by a very low fluence phytochrome response; the involvement of a blue light/UV-A and a UV-B photoreceptor is also possible [7].

Associations of SLC7A3 with chemical compounds

• This is in contrast to rat and murine CAT-3 proteins that have been reported to display a very low activity and to be inhibited by neutral and anionic L-amino acids as well as D-arginine (Hosokawa, H., et al. (1997) J. Biol. Chem. 272, 8717-8722; Ito, K., and Groudine, M. (1997) J. Biol. Chem. 272, 26780-26786) [10].
• In young leaves, only Cat1 and Cat3 transcripts increase in response to wounding, but JA does not play a role [11].

Other interactions of SLC7A3

• Western-blot analysis of biotinylated surface proteins demonstrated a PMA-induced decrease in hCAT-3 in the plasma membrane, but not in total protein lysates [1].

Analytical, diagnostic and therapeutic context of SLC7A3

• On the Northern blot of adult rat tissues, the expression of CAT3 is restricted to the brain [12].
• In the present study, cellular localization of CAT3 mRNA and protein in the adult rat brain sections was examined by in situ hybridization with cRNA and immunostaining with a CAT3-specific antiserum, respectively [12].

References