Biology subjects

Witucki, L.

Publications and source records attributed to Witucki, L..

3 recordsLinked to original sources

bioRxiv2023

Homocysteine Metabolites Impair the Phf8/H4K20me1/mTOR/Autophagy Pathway by Upregulating the Expression of PHF8-targeting miR-22-3p and miR-1229-3p in Human Vascular Endothelial Cells

The inability to efficiently metabolize homocysteine (Hcy) due to nutritional and genetic deficiencies, leads to hyperhomocysteinemia (HHcy) and endothelial dysfunction, a hallmark of atherosclerosis which underpins cardiovascular disease (CVD). PHF8 is a histone demethylase that demethylates H4K20me1, which affects the mammalian target of rapamycin (mTOR) signaling and autophagy, processes that play important roles in CVD. PHF8 is regulated by microRNA (miR) such as miR-22-3p and miR-1229-3p. Biochemically, HHcy is characterized by elevated levels of Hcy, Hcy-thiolactone and N-Hcy-protein. Here, we examined effects of these metabolites on miR-22-3p, miR-1229-3p, and their target PHF8, as well as on the downstream consequences of these effects on H4K20me1, mTOR-, and autophagy-related proteins and mRNAs expression in human umbilical vein endothelial cells (HUVEC). We found that treatments with N-Hcy-protein, Hcy-thiolactone, or Hcy upregulated miR-22-3p and miR-1229-3p, attenuated PHF8 expression, upregulated H4K20me1, mTOR, and phospho-mTOR. Autophagy-related proteins (BECN1, ATG5, ATG7, lipidated LC3-II, and LC3-II/LC3-I ratio) were significantly downregulated by at least one of these metabolites. We also found similar changes in the expression of miR-22-3p, Phf8, mTOR- and autophagy-related proteins/mRNAs in vivo in hearts of Cbs-/- mice, which show severe HHcy and endothelial dysfunction. Treatments with inhibitors of miR-22-3p or miR-1229-3p abrogated the effects of Hcy-thiolactone, N-Hcy-protein, and Hcy on miR expression and on PHF8, H4K20me1, mTOR-, and autophagy-related proteins/mRNAs in HUVEC. Taken together, these findings show that Hcy metabolites upregulate miR-22-3p and miR-1229-3p expression, which then dysregulate the PHF8/H4K20me1/mTOR/autophagy pathway, important for vascular homeostasis.

biochemistry↗

bioRxiv2023

Homocysteine Metabolites Inhibit Autophagy and Elevate Amyloid Beta by Impairing Phf8/H4K20me1-dependent Epigenetic Regulation of mTOR in Cystathionine Beta-Synthase-Deficient Mice

The loss of cystathionine {beta}-synthase (CBS), an important homocysteine (Hcy)-metabolizing enzyme or the loss of PHF8, an important histone demethylase participating in epigenetic regulation, causes severe mental retardation in humans. Similar neuropathies were also observed in Cbs-/- and Phf8-/- mice. How CBS or PHF8 depletion can cause neuropathy was unknown. To answer this question, we examined a possible interaction between PHF8 and CBS using Cbs-/- mouse and neuroblastoma cell models. We quantified gene expression by RT-qPCR and Western blotting, mTOR-bound H4K20me1 by chromatin immunoprecipitation (CHIP) assay, and amyloid {beta} (A{beta}) by confocal fluorescence microscopy using anti-A{beta} antibody. We found significantly reduced expression of Phf8, increased H4K20me1, increased mTOR expression and phosphorylation, and increased App, both on protein and mRNA levels in brains of Cbs-/- mice vs. Cbs+/- sibling controls. Autophagy-related proteins Becn1, Atg5, and Atg7 were downregulated while p62 was upregulated on protein and mRNA levels, suggesting impaired autophagy in Cbs-/- brains. In mouse neuroblastoma N2a or N2a-APPswe cells, treatments with Hcy-thiolactone, N-Hcy-protein or Hcy, or Cbs gene silencing by RNA interference significantly reduced Phf8 expression and increased total H4K20me1 as well as mTOR promoter-bound H4K20me1. This led to transcriptional mTOR upregulation, autophagy downregulation, and significantly increased App and A{beta} levels. The Phf8 gene silencing increased A{beta}, but not App, levels. Taken together, our findings identify Phf8 as a regulator of A{beta} synthesis and suggest that neuropathy of Cbs deficiency is mediated by Hcy metabolites, which transcriptionally dysregulate the Phf8->H4K20me1->mTOR->autophagy pathway thereby increasing A{beta} accumulation.

biochemistry↗

bioRxiv2023

Depletion of bleomycin hydrolase (Blmh) downregulates histone demethylase Phf8, impairs mTOR signaling/autophagy, accelerates amyloid beta accumulation, and induces neurological deficits in mice

Bleomycin hydrolase (BLMH), a homocysteine (Hcy)-thiolactone detoxifying enzyme, is attenuated in brains of Alzheimers disease patients. In mice, Blmh depletion causes astrogliosis and behavioral changes. Depletion of histone demethylase PHF8, which controls mTOR signaling by demethylating H4K20me1, causes neuropathy in humans and mice. Here we examined how Blmh depletion affects the Phf8/H4K20me1/mTOR signaling/autophagy pathway and amyloid beta (A{beta}) accumulation and cognitive/neuromotor performance in mice. We found that Phf8 was significantly downregulated in brains of Blmh-/- mice vs. Blmh+/+ sibling controls. H4K20me1, mTOR, phospho-mTOR, and App were upregulated while autophagy markers Bcln1, Atg5, and Atg7 were downregulated in Blmh-/- brains. Blmh depletion caused similar biochemical changes and significantly elevated A{beta} in Blmh-/-5xFAD vs. Blmh+/+5xFAD brains. Behavioral testing identified cognitive/neuromotor deficits in Blmh-/- and Blmh-/-5xFAD mice. In Blmh-depleted N2a-APPswe cells, Phf8 was downregulated, while APP, total H4K20me1, and H4K20me1-mTOR promoter binding were elevated. This led to mTOR upregulation, autophagy downregulation, and significantly increased APP and A{beta} levels. Phf8 depletion or treatments with Hcy-thiolactone or N-Hcy-protein, metabolites that are elevated in Blmh-depleted mice, induced similar biochemical changes in N2a-APPswe cells, akin to those in induced by Blmh depletion. Taken together, our findings indicate that Blmh interacts with APP and the Phf8/H4K20me1/mTOR/autophagy pathway and show that disruption of these interactions lead to A{beta} accumulation and cognitive and neuromotor deficits.

biochemistry↗