SNAT2 transceptor signalling via mTOR A role in cell growth and proliferation

Abstract

Introduction 3. Materials 3.1 Materials 3.2 Cell Culture 3.3 Analysis of cell number, size and intracellular amino acids 3.4 SDS-PAGE and immunoblotting 3.5 Measurement of System A uptake 3.6 Proteomic analysis of TAP-tagged SNAT2 complexes 3.7 Statistical analysis 4. Results 4.1 MCF-7 cells express SNAT1, SNAT2 and exhibit functional System A transport 4.2 Effects of sustained System A inhibition on cell growth and proliferation 4.3 Chronic cell incubation with Me-AIB and intracellular amino acid levels 4.4 System A-induced modulation of mTOR signalling 4.5 Analysis of TAP-tagged SNAT2 protein complexes 5. Discussion 6. Acknowledgment 7. References Abbreviations: Methyl aminoisobutyrate, Me-AIB; mTORC, mammalian target of rapamycin complex; TAP, tandem affinity purification; MLCK, myosin light chain kinase; BCAA, branched chain amino acids.

A GC-MS/Single-Cell Method to Evaluate Membrane Transporter Substrate Specificity and Signaling

“…Alternatively, SNAT2 could mediate accumulation of amino acids via tertiary active transport involving endogenously expressed transporters which then could activate mTORC1. Our results support the notion that SNAT2 represents a likely candidate as an important mTORC1 activator/accelerator as has been previously proposed (Hyde et al, 2007;Baird et al, 2009;Pinilla et al, 2011;Poncet and Taylor, 2013;Broer and Broer, 2017;Broer, 2018;Hoffmann et al, 2018). The activation of mTORC1 by SNAT2 represents an alternative mechanism to the long-suggested combined action of the amino acid transporters LAT1 and ASCT2 (Nicklin et al, 2009).…”

“…The method developed here can also be used to investigate amino acid signaling, the components of which are highly conserved in multicellular eukaryotes (Panchaud et al, 2013;Saxton and Sabatini, 2017;Tatebe and Shiozaki, 2017;Javed and Fairweather, 2019). Our results support the concept of SNAT2 as a transceptor (Pinilla et al, 2011), because mTORC1 activation was observed at time points where cytosolic leucine was barely increased. Another SNAT2 substrate glutamine has also been shown to activate mTORC1 in HepG2 and HeLa cells independent of the cytosolic Leu concentration, also suggesting SNAT2 can activate mTORC1 as a transceptor using glutamine (Chiu et al, 2012).…”

“…However, ASCT2 knockout studies in several cell lines have failed to observe a reduction of mTORC1 activity (Broer et al, 2000;Bode et al, 2002;Broer et al, 2016). SNAT2 and Golgi localized PAT4 have been suggested as mTORC1 activators by acting as membrane 'transceptors', where extracellular binding of substrate and allosterically-mediated signal transduction causes activation of mTORC1 (Goberdhan et al, 2005;Pinilla et al, 2011;Fan et al, 2016). For leucine, however, the transceptor mechanism appears unlikely as leucine-mediated mTORC1 activation has been shown to require an intracellular leucine increase (Christie et al, 2002;Beugnet et al, 2003).…”

Synaptojanin1 deficiency upregulates basal autophagosome formation in astrocytes

“…Our study suggests that glucose sensing plays a crucial role in regulating the basal level astrocyte autophagy ( 34 , 35 , 36 ). The recycling of the glucose transporter on the plasma membrane is a dynamic and highly regulated process.…”

Identification of Ftr1 and Zrt1 as iron and zinc micronutrient transceptors for activation of the PKA pathway in Saccharomyces cerevisiae

“…Transceptors have been identified in other organisms, such as GT1 in Leishmania mexicana 57 and GLUT2 in mice 585960. Finally, the concept of transceptors has also emerged in human cells with the identification of h CNT1 61 and h SNAT2 626364. Hence, the concept of transceptors seems to be conserved throughout evolution in eukaryotic organisms.…”