1.γ-aminobutyric acid type A (GABAA) receptor subunits play a direct structural role in synaptic contact formation via their N-terminal extracellular domains.
Brown LE1, Nicholson MW2, Arama JE1, Mercer A1, Thomson AM1, Jovanovic JN3. J Biol Chem. 2016 Apr 20. pii: jbc.M116.714790. [Epub ahead of print]
The establishment of cell-cell contacts between presynaptic GABAergic neurons and their postsynaptic targets initiates the process of GABAergic synapse formation. GABAA receptors (GABAARs), the main postsynaptic receptors for GABA, have been recently demonstrated to act as synaptogenic proteins that can single-handedly induce the formation and functional maturation of inhibitory synapses. To establish how the subunit composition of GABAARs influences their ability to induce synaptogenesis, a co-culture model system incorporating GABAergic medium spiny neurons (MSNs) and the HEK293 cells, stably expressing different combinations of receptor subunits, was developed. Analyses of HEK293 cells innervation by MSN axons using immunocytochemistry, activity-dependent labeling and electrophysiology have indicated that γ2 subunit is required for the formation of active synapses and that its effects are influenced by the type of α/β subunits incorporated into the functional receptor.
2.Structural evidence of the species-dependent albumin binding of the modified cyclic phosphatidic acid with cytotoxic properties.
Sekula B1, Ciesielska A1, Rytczak P1, Koziolkiewicz M1, Bujacz A2. Biosci Rep. 2016 Apr 15. pii: BSR20160089. [Epub ahead of print]
Cyclic phosphatidic acids (cPAs) are naturally occurring, very active signaling molecules, which are involved in several pathological states, such as cancer, diabetes, or obesity. As molecules of highly lipidic character found in the circulatory system, cPAs are bound and transported by the main extracellular lipid binding protein - serum albumin.<br />Here, we present the detailed interactions between human serum albumin (HSA) and equine serum albumin (ESA) with a derivative of cPA, 1-O-myristoyl-sn-glycerol-2,3-cyclic phosphorodithioate (Myr-2S-cPA). Initial selection of the ligand used for the structural study was made by the analysis of the therapeutically promising properties of the sulfur containing analogues of cPA in respect to the unmodified lysophospholipids. Substitution of one or two non-bridging oxygen atoms in the phosphate group with one or two sulfur atoms increases the cytotoxic effect of cPAs up to 60% on the human prostate cancer cells.
3.Deletion of Amino Acid Transporter ASCT2 (SLC1A5) Reveals an Essential Role for Transporters SNAT1 (SLC38A1) and SNAT2 (SLC38A2) to Sustain Glutaminolysis in Cancer Cells.
Bröer A1, Rahimi F1, Bröer S2. J Biol Chem. 2016 Apr 26. pii: jbc.M115.700534. [Epub ahead of print]
Many cancer cells depend on glutamine as they use the glutaminolysis pathway to generate building blocks and energy for anabolic purposes. As a result, glutamine transporters are essential for cancer growth and are potential targets for cancer chemotherapy, with ASCT2 (SLC1A5) being investigated most intensively. Here we show that HeLa epithelial cervical cancer cells and 143B osteosarcoma cells express a set of glutamine transporters including SNAT1 (SLC38A1), SNAT2 (SLC38A2), SNAT4 (SLC38A4), LAT1 (SLC7A5), and ASCT2 (SLC1A5). Net glutamine uptake did not depend on ASCT2, but required expression of SNAT1 and SNAT2. Deletion of ASCT2, did not reduce cell growth but caused an amino acid starvation response and up-regulation of SNAT1 to replace ASCT2 functionally. Silencing of GCN2 in the ASCT2 (-/-) background reduced cell growth, showing that a combined targeted approach would inhibit growth of glutamine-dependent cancer cells.
