Structure-based development of potent and selective type-II kinase inhibitors of RIPK1.

Receptor-interacting serine/threonine-protein kinase 1 (RIPK1) functions as a key regulator in inflammation and cell death and is involved in mediating a variety of inflammatory or degenerative diseases. A number of allosteric RIPK1 inhibitors (RIPK1i) have been developed, and some of them have already advanced into clinical evaluation. Recently, selective RIPK1i that interact with both the allosteric pocket and the ATP-binding site of RIPK1 have started to emerge.

Prolonged hypoxia alleviates prolyl hydroxylation-mediated suppression of RIPK1 to promote necroptosis and inflammation.

The prolyl hydroxylation of hypoxia-inducible factor 1α (HIF-1α) mediated by the EGLN-pVHL pathway represents a classic signalling mechanism that mediates cellular adaptation under hypoxia. Here we identify RIPK1, a known regulator of cell death mediated by tumour necrosis factor receptor 1 (TNFR1), as a target of EGLN1-pVHL. Prolyl hydroxylation of RIPK1 mediated by EGLN1 promotes the binding of RIPK1 with pVHL to suppress its activation under normoxic conditions.

Metabolic orchestration of cell death by AMPK-mediated phosphorylation of RIPK1.

Adenosine monophosphate-activated protein kinase (AMPK) activity is stimulated to promote metabolic adaptation upon energy stress. However, sustained metabolic stress may cause cell death. The mechanisms by which AMPK dictates cell death are not fully understood.

Context-dependent requirement of G protein coupling for Latrophilin-2 in target selection of hippocampal axons.

The formation of neural circuits requires extensive interactions of cell-surface proteins to guide axons to their correct target neurons. -cellular interactions of the adhesion G protein-coupled receptor latrophilin-2 (Lphn2) with its partner teneurin-3 instruct the precise assembly of hippocampal networks by reciprocal repulsion. Lphn2 acts as a repulsive receptor in distal CA1 neurons to direct their axons to the proximal subiculum, and as a repulsive ligand in the proximal subiculum to direct proximal CA1 axons to the distal subiculum.

Core transcription programs controlling injury-induced neurodegeneration of retinal ganglion cells.

Regulatory programs governing neuronal death and axon regeneration in neurodegenerative diseases remain poorly understood. In adult mice, optic nerve crush (ONC) injury by severing retinal ganglion cell (RGC) axons results in massive RGC death and regenerative failure. We performed an in vivo CRISPR-Cas9-based genome-wide screen of 1,893 transcription factors (TFs) to seek repressors of RGC survival and axon regeneration following ONC.

Utilizing mouse optic nerve crush to examine CNS remyelination.

In developing pro-myelination treatment, an important hurdle is the lack of reliable animal models for assessing de novo myelination in disease settings. We recently showed that regenerated axons in injured optic nerves fail to be myelinated, providing an animal model for this purpose. Here, we describe procedures to promote axonal regeneration, administer optic nerve crush, and assess oligodendrocyte differentiation and maturation into myelination-competent oligodendrocytes.

Discovery of a cooperative mode of inhibiting RIPK1 kinase.

RIPK1, a death domain-containing kinase, has been recognized as an important therapeutic target for inhibiting apoptosis, necroptosis, and inflammation under pathological conditions. RIPK1 kinase inhibitors have been advanced into clinical studies for the treatment of various human diseases. One of the current bottlenecks in developing RIPK1 inhibitors is to discover new approaches to inhibit this kinase as only limited chemotypes have been developed.

Robust Myelination of Regenerated Axons Induced by Combined Manipulations of GPR17 and Microglia.

Myelination facilitates rapid axonal conduction, enabling efficient communication across different parts of the nervous system. Here we examined mechanisms controlling myelination after injury and during axon regeneration in the central nervous system (CNS). Previously, we discovered multiple molecular pathways and strategies that could promote robust axon regrowth after optic nerve injury.

Microglia-organized scar-free spinal cord repair in neonatal mice.

Spinal cord injury in mammals is thought to trigger scar formation with little regeneration of axons. Here we show that a crush injury to the spinal cord in neonatal mice leads to scar-free healing that permits the growth of long projecting axons through the lesion. Depletion of microglia in neonatal mice disrupts this healing process and stalls the regrowth of axons, suggesting that microglia are critical for orchestrating the injury response.

TBK1 Suppresses RIPK1-Driven Apoptosis and Inflammation during Development and in Aging.

Aging is a major risk factor for both genetic and sporadic neurodegenerative disorders. However, it is unclear how aging interacts with genetic predispositions to promote neurodegeneration. Here, we investigate how partial loss of function of TBK1, a major genetic cause for amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) comorbidity, leads to age-dependent neurodegeneration.

Death-domain dimerization-mediated activation of RIPK1 controls necroptosis and RIPK1-dependent apoptosis.

RIPK1 is a critical mediator of cell death and inflammation downstream of TNFR1 upon stimulation by TNFα, a potent proinflammatory cytokine involved in a multitude of human inflammatory and degenerative diseases. RIPK1 contains an N-terminal kinase domain, an intermediate domain, and a C-terminal death domain (DD). The kinase activity of RIPK1 promotes cell death and inflammation.

PELI1 functions as a dual modulator of necroptosis and apoptosis by regulating ubiquitination of RIPK1 and mRNA levels of c-FLIP.

Apoptosis and necroptosis are two distinct cell death mechanisms that may be activated in cells on stimulation by TNFα. It is still unclear, however, how apoptosis and necroptosis may be differentially regulated. Here we screened for E3 ubiquitin ligases that could mediate necroptosis.

Modification of BECN1 by ISG15 plays a crucial role in autophagy regulation by type I IFN/interferon.

ISG15 (ISG15 ubiquitin-like modifier), a ubiquitin-like protein, is one of the major type I IFN (interferon) effector systems. ISG15 can be conjugated to target proteins (ISGylation) via the stepwise action of E1, E2, and E3 enzymes. Conjugated ISG15 can be removed (deISGylated) from target proteins by USP18 (ubiquitin-specific peptidase 18).

Synthesis, SAR and biological evaluation of natural and non-natural hydroxylated and prenylated xanthones as antitumor agents.

In order to explore the detailed structure-activity relationship (SAR) around xanthone scaffold bearing hydroxyl and prenyl moieties, twenty-nine natural and non-natural hydroxylated and prenylated xanthones have been synthesized and evaluated for their in vitro anti-proliferative activities against five human cancer cell lines, including HepG2 (hepatocelluar carcinoma), HCT-116 (colon carcinoma), A549 (lung carcinoma), BGC823 (gastric carcinoma) and MDAMB- 231 (breast carcinoma). The SAR analysis revealed that the anti-proliferative activity of the xanthones is substantially influenced by the position and number of attached hydroxyl and prenyl groups, and the presence of hydroxyl group ortho to the carbonyl function of xanthone scaffold contributes significantly to their cytotoxicity. The new prenylated xanthone 20 with a relatively simple structure, namely 1,3,8-trihydroxy-2-prenylxanthone, was found to exhibit potent antitumor activities comparable to α-mangostin against all the five cancer cell lines.