Biology subjects

Abramson, E.

Publications and source records attributed to Abramson, E..

3 recordsLinked to original sources

bioRxiv2021

D-cysteine is an endogenous regulator of neural progenitor cell dynamics in the mammalian brain

D-amino acids are increasingly recognized as important signaling molecules in the mammalian central nervous system. However, the D-stereoisomer of the amino acid with the fastest in vitro spontaneous racemization rate, cysteine, has not been examined in mammals. Using chiral high-performance liquid chromatography and an stereospecific luciferase assay, we identify endogenous D-cysteine in the mammalian brain. We identify serine racemase (SR), which generates the NMDA glutamate receptor co-agonist D-serine, as a candidate biosynthetic enzyme for D-cysteine. Levels of D-cysteine are enriched over twentyfold in the embryonic mouse brain compared to the adult. D-cysteine reduces the proliferation of cultured mouse embryonic neural progenitor cells (NPCs) by approximately 50%, effects not shared with D-serine or L-cysteine. The antiproliferative effect of D-cysteine is mediated by the transcription factors FoxO1 and FoxO3a. The selective influence of D-cysteine on NPC proliferation is reflected in overgrowth and aberrant lamination of the cerebral cortex in neonatal SR knockout mice. Finally, we perform an unbiased screen for D-cysteine-binding proteins in NPCs by immunoprecipitation with a D-cysteine-specific antibody followed by mass spectrometry. This approach identifies myristoylated alanine-rich C-kinase substrate (MARCKS) as a putative D-cysteine-binding protein. Together, these results establish endogenous mammalian D-cysteine and implicate it as a physiologic regulator of NPC homeostasis in the developing brain.

neuroscience↗

bioRxiv2020

Loss of PI3-kinase activity of inositol polyphosphate multikinase impairs PDK1-mediated AKT activation, cell migration, and intestinal homeostasis

Inositol polyphosphate multikinase (IPMK) is a rate-limiting enzyme in the inositol phosphate (IP) pathway which converts IP3 to IP4 and IP5. In mammalian cells, IPMK can also act as a phosphoinositol-3-kinase (PI3-kinase). We previously found that IPMK is a critical PI3-kinase activator of AKT. Here, we show that IPMK mediates AKT activation by promoting membrane localization and activation of PDK1. The PI3-kinase activity of IPMK is dispensable for membrane localization of AKT, which is entirely controlled by classical PI3-kinase (p110,{beta},{gamma} , {delta}). By contrast, we found that PDK1 membrane localization was largely independent of classical PI3-kinase. Membrane localization of PDK1 stimulates cell migration by dissociating ROCK1 from inhibitory binding to RhoE and promoting ROCK1-mediated myosin light chain (MLC) phosphorylation. Deletion of IPMK impairs cell migration associated with the abolition of PDK1-mediated ROCK1 disinhibition and subsequent MLC phosphorylation. To investigate the physiological relevance of IPMK-mediated AKT activation, we generated mice selectively lacking IPMK in epithelial cells of the intestine, where IPMK is highly expressed. Deletion of IPMK in intestinal epithelial cells markedly reduced AKT phosphorylation and diminished numbers of Paneth cells - a crypt-resident epithelial cell type that generates the physiological niche for intestinal stem cells. Ablation of IPMK impaired intestinal epithelial cell regeneration basally and after; chemotherapy-induced damage, suggesting a broad role for IPMK in the activation of AKT and intestinal tissue regeneration. In summary, the PI3-kinase activity of IPMK promotes membrane localization of PDK1, a critical kinase whereby AKT maintains intestinal homeostasis. One Sentence SummaryPI3-kinase activity of IPMK is essential for activation of AKT.

cell biology↗

bioRxiv2020

Designed PKC-targeting bryostatin analogs modulate innate immunity and neuroinflammation

Neuroinflammation characterizes multiple neurologic diseases, including primary inflammatory conditions such as multiple sclerosis (MS) and classical neurodegenerative diseases. Aberrant activation of the innate immune system contributes to disease progression in these conditions, but drugs that modulate innate immunity, particularly within the central nervous system (CNS), are lacking. The CNS-pene-trant natural product bryostatin-1 (bryo-1) attenuates neuroinflammation by targeting innate myeloid cells. Supplies of natural bryo-1 are limited but a recent scalable synthesis has enabled access to it and its analogs (termed bryologs), the latter providing a path to more efficacious, better tolerated, and more accessible agents. Here, we show that multiple synthetically accessible bryologs replicate the anti-inflammatory effects of bryo-1 on innate immune cells in vitro, and a lead bryolog attenuates neuroinflammation in vivo - actions mechanistically dependent on PKC binding. Our findings identify bryologs as promising drug candidates for targeting innate immunity in neuroinflammation and create a platform for evaluation of synthetic PKC modulators in neuroinflammatory diseases such as MS. Graphical Abstract O_FIG_DISPLAY_L [Figure 1] M_FIG_DISPLAY C_FIG_DISPLAY

immunology↗