Figure 1.
FAS receptor pathway in peripheral cells [76].
The membrane FAS-R (blue) forms a trimer upon ligand binding (TNFSF13, red). The adaptor molecule FADD (green) then binds to the death domain of FAS-R through its own death domain. The amino terminus of FADD facilitates binding to caspase-8 (maroon oval). Caspase-8 self-activates through proteolytic cleavage into active caspase subunits, which can cleave other effector caspases (3, 6, 9), eventually leading to DNA degradation, membrane blebbing, and other hallmarks of apoptosis. In most cell types (Type II), caspase-8 catalyzes the cleavage of the pro-apoptotic BH3-only protein BID (orange) into its truncated form, tBID. tBID engages anti-apoptotic members of the family (e.g. BCL-2), allowing pro-apoptotic members (e.g. BAX) to translocate to the outer mitochondrial membrane, thus permeabilizing the membrane and facilitating release of pro-apoptotic proteins such as cytochrome c (tan). Cytochrome c release reinforces the cellular apoptotic drive through the intrinsic apoptotic pathway. Death receptors 4/5 (TNFSF10) appear to have identical intracellular pathway signaling to FAS receptor [76].
Table 1.
Genes analyzed with ABI Taqman Gene Expression assay part numbers.
Figure 2.
Gene expression levels of TNFSF13-FAS receptor pathway genes of interest relative to three housekeeping genes in dorsolateral prefrontal cortex from patients with schizophrenia.
cDNA samples obtained from the combined SMRI and NSW TRC collections from individuals with schizophrenia and unaffected controls were subjected to qRT-PCR. Expressions of TNFSF13 (A), FAS receptor (C), CFLARpan (E), CFLARlong (F) and BID (G) relative to three housekeeping genes (β-actin, TATA box binding protein and ubiquitin C) were calculated using the deltadelta Ct method. Horizontal lines indicate the population median, except for panel (G) where they indicate the mean as those data were normally distributed. Frequency distributions for TNFSF13, FAS receptor and BID are displayed in panels (B), (D), and (H). ** p<0.01.
Figure 3.
Gene expression levels of TNFSF13-FAS receptor pathway genes of interest relative to three housekeeping genes in dorsolateral prefrontal cortex from patients with bipolar disorder.
cDNA samples obtained from the SMRI collection from individuals with bipolar disorder and unaffected controls were subjected to qRT-PCR. Expressions of TNFSF13 (A), FAS receptor (B), BID (C), CFLARpan (D), and CFLARlong (E) relative to three housekeeping genes (β-actin, TATA box binding protein and ubiquitin C) were calculated using the deltadelta Ct method. Horizontal lines indicate the population median, except for panel (E) where they indicate the mean as those data were normally distributed. * p<0.05.
Figure 4.
Gene expression levels of TNFSF13, FAS receptor and BID relative to three housekeeping genes in OFC from patients with schizophrenia, patients with bipolar disorder and unaffected controls.
cDNA samples from individuals with schizophrenia, bipolar disorder and unaffected controls were subjected to qRT-PCR. Expressions of TNFSF13 (A), FAS receptor (B) and BID (C) relative to three housekeeping genes (β-actin, TATA box binding protein and ubiquitin C) were calculated using the deltadelta Ct method. Horizontal lines indicate the population median, except for panel (C) where they indicate the mean as those data were normally distributed.
Table 2.
Variance (R2) in parvalbumin, somatostatin, PPP1R9B and DLG4 mRNA transcript levels accounted for by TNFSF13 expression and tissue pH in the NSW TRC collection.
Table 3.
Relationship of gene expression in the DLPFC with demographic and clinical variables.
Figure 5.
The effect of TNFSF13 exposure on intracellular pH, and of decreased intracellular pH on TNFSF13 and FAS receptor gene expression.
Intracellular pH of U-87 MG cells was artificially decreased using nigericin and phosphate buffer to pH 6.4, 6.9 and 7.3 for 0.5, 3, 12 or 24 hours and transcript levels of the TNFSF13 (A) or FAS receptor (B) genes measured by qRT-PCR. Expression levels were calculated relative to three housekeeping genes (β-actin, TATA box binding protein and ubiquitin C) using the deltadelta Ct method. aTranscript levels at the 0.5 hours time point were significantly greater than at all other time points, bDecreasing pH significantly suppressed transcript levels of TNFSF13, cThere was no significant effect of pH on FAS receptor transcripts. U-87 MG glioblastoma cell cultures were treated with TNFSF13 (1 pg or 100 pg TNFSF13/microliter of culture media) for up to 48 hours and the intracellular pH determined (C). *p<0.05, ***p<0.001.
Table 4.
Demographic and clinical variables of the combined SMRI and NSW TRC collection.