Biology subjects

Meador-Woodruff, J. H.

Publications and source records attributed to Meador-Woodruff, J. H..

4 recordsLinked to original sources

bioRxiv2019

Protein expression of prenyltransferase subunits in postmortem schizophrenia dorsolateral prefrontal cortex

The pathophysiology of schizophrenia includes altered neurotransmission, dysregulated intracellular signaling pathway activity, and abnormal dendritic morphology that contribute to deficits of synaptic plasticity in the disorder. These processes all require dynamic protein-protein interactions at cell membranes. Lipid modifications target proteins to membranes by increasing substrate hydrophobicity by the addition of a fatty acid or isoprenyl moiety, and recent evidence suggests that dysregulated post-translational lipid modifications may play a role in multiple neuropsychiatric disorders including schizophrenia. Consistent with these emerging findings, we have recently reported decreased protein S-palmitoylation in schizophrenia. Protein prenylation is a lipid modification that occurs upstream of S-palmitoylation on many protein substrates, facilitating membrane localization and activity of key intracellular signaling proteins. Accordingly, we hypothesized that in addition to palmitoylation, protein prenylation may be abnormal in schizophrenia. To test this, we assayed protein expression of the five prenyltransferase subunits (FNTA, FNTB, PGGT1B, RABGGTA, and RABGGTB) in postmortem dorsolateral prefrontal cortex from patients with schizophrenia and paired comparison subjects (N = 13 pairs). We found decreased levels of FNTA (14%), PGGT1B (13%), and RABGGTB (8%) in schizophrenia. To determine if upstream or downstream factors may be driving these changes, we also assayed protein expression of the isoprenoid synthases FDPS and GGPS1, and prenylation-dependent processing enzymes REC and ICMT. We found these upstream and downstream enzymes to have normal protein expression. To rule out effects from chronic antipsychotic treatment, we assayed FNTA, PGGT1B and RABGGTB in cortex from rats treated long-term with haloperidol decanoate, and found no change in the expression of these proteins. Given the role prenylation plays in localization of key signaling proteins found at the synapse, these data offer a potential mechanism underlying abnormal protein-protein interactions and protein localization in schizophrenia.

neuroscience↗

bioRxiv2019

Altered protein expression of galactose and N-acetylgalactosamine transferases in schizophrenia superior temporal gyrus

Abnormal glycosylation in schizophrenia brain has been previously implicated in disruptions to protein trafficking, localization, and function. Glycosylation is an enzyme-mediated posttranslational modification and, along with reports of altered glycan biosynthesis and abnormal glycan levels in peripheral fluids, growing evidence for altered glycosylation pathway activity in schizophrenia prompted investigation of specific enzymes which may be responsible for these abnormalities. Glycosylation is a highly variable yet tightly controlled cellular process and, depending on the molecule(s) affected, altered glycan modifications can influence the trajectory of many key functional pathways. In a preliminary gene array study, abnormal transcript expression of 36 glycosylation-associated enzymes was identified in schizophrenia brain. Subsequently, protein expression abnormalities of enzymes which act on glucose (UGGT2), mannose (EDEM2), fucose (FUT8, POFUT2), and N-acetylglucosamine (MGAT4A, B3GNT8) have been reported in this illness. The current study investigates protein expression levels by western blot analysis of the galactose and N-acetylgalactosamine (GalNAc) transferases B3GALTL1, B4GALT1, C1GALT1, GALNT2, GALNT7, GALNT16, and GALNTL5, as well as a related chaperone protein, COSMC, in superior temporal gyrus of age- and sex-matched pairs of schizophrenia and non-psychiatrically ill comparison subjects (N = 16 pairs). In schizophrenia, reduced {beta}-1,4-galactosyltransferase 1 (B4GALT1) and polypeptide GalNAc-transferase 16 (GALNT16) were identified. These findings add support to the hypothesis that dysregulated glycosylation-associated enzyme expression contributes to altered protein glycosylation and downstream substrate-specific defects in schizophrenia.

neuroscience↗

bioRxiv2018

Increased α-2,8-sialyltransferase 8B (ST8SIA2) expression in schizophrenia superior temporal gyrus

Reduced polysialylation of neural cell adhesion molecule (NCAM) in schizophrenia has been suggested to contribute to abnormal neuroplasticity and neurodevelopmental features of this illness. The posttranslational addition of sialic acid is mediated by sialyltransferases, and polysialylation (the addition of [≥] 8 -2,8-linked sialic acid residues) is catalyzed by three enzymes: ST8SIA2 (also called STX), ST8SIA4 (also called PST), and/or ST8SIA3. ST8SIA2 and ST8SIA4 are the primary mediators of NCAM polysialylation. The gene encoding ST8SIA2 maps to schizophrenia risk locus 15q26, and single nucleotide polymorphisms (SNPs) and SNP haplotypes of the ST8SIA2 gene have been associated with schizophrenia in multiple populations. The current study in elderly schizophrenia (N = 16) and comparison (N = 14) subjects measured the protein expression of NCAM, polysialylated-NCAM (PSANCAM), and three poly--2,8-sialyltransferases (ST8SIA2, ST8SIA3, and ST8SIA4) in postmortem superior temporal gyrus. Although expression of NCAM, PSA-NCAM, ST8SIA3, and ST8SIA4 were not different in schizophrenia, increased protein levels of ST8SIA2 were identified. It has been reported that ST8SIA2 mutations associated with increased schizophrenia risk impair PSA-NCAM synthesis, suggesting that increased protein expression of ST8SIA2 may represent a compensatory mechanism in the face of impaired enzyme function. This interpretation is further supported by our finding that the relationship between ST8SIA2 enzyme expression and PSA-NCAM levels are different between schizophrenia and comparison subjects. Together these findings suggest a possible neurodevelopmentally-regulated mechanism which could contribute to abnormal synaptic plasticity evident in schizophrenia.

neuroscience↗

bioRxiv2018

Glycosylation enzyme mRNA expression in dorsolateral prefrontal cortex of elderly patients with schizophrenia: Evidence for dysregulation of multiple glycosylation pathways

Altered protein post-translational modifications such as glycosylation have become a target of investigation in the pathophysiology of schizophrenia. Disrupted glycosylation associated processes including atypical sphingolipid metabolism, reduced polysialylation of cell adhesion molecules, abnormal proteoglycan expression, and irregular glycan synthesis and branching have also been reported in this disorder. These pathways are regulated by the expression of glycosidases and glycosyltransferases, classes of enzymes which comprise approximately 2% of the genome. Many glycosylation enzymes can participate in multiple glycosylation pathways and dysregulation of enzyme expression could represent a common mechanism leading to a variety of glycan processing deficits in schizophrenia. In matched pairs of elderly schizophrenia and comparison subject (N = 12 pairs) dorsolateral prefrontal cortex, we measured mRNA levels of 84 key glycosylation enzymes by qPCR array. We found dysregulated transcript expression of 36 glycosylation enzymes from 12 functional categories. All of the abnormally expressed enzymes demonstrated increased transcript expression in schizophrenia, and many altered enzymes are known to modify substrates that have been previously implicated in the pathophysiology this illness. These findings suggest that abnormal glycosylation enzyme expression in schizophrenia may contribute to dysregulation of multiple glycosylation pathways, and disruptions of these central cell signaling processes may underlie a variety of deficits in schizophrenia.

neuroscience↗