Faculty Bibliography

Atherosclerosis results from lipid-driven inflammation of the arterial wall that fails to resolve. Imbalances in macrophage accumulation and function, including diminished migratory capacity and defective efferocytosis, fuel maladaptive inflammation and plaque progression. The neuroimmune guidance cue netrin-1 has dichotomous roles in inflammation partly due to its multiple receptors; in atherosclerosis, netrin-1 promotes macrophage survival and retention via its receptor Unc5b. To minimize the pleiotropic effects of targeting netrin-1, we tested the therapeutic potential of deleting Unc5b in mice with advanced atherosclerosis. We generated Unc5b

Although the concept that the blood-brain barrier (BBB) plays an important role in the etiology and pathogenesis of Alzheimer's disease (AD) has become increasingly accepted, little is known yet about how it actually contributes. We and others have recently identified a novel functionally distinct subset of BBB pericytes (PCs). In the present study, we sought to determine whether these PC subsets differentially contribute to AD-associated pathologies by immunohistochemistry and amyloid beta (Aβ) peptidomics. We demonstrated that a disease-associated PC subset (PC2) expanded in AD patients compared to age-matched, cognitively unimpaired controls. Surprisingly, we found that this increase in the percentage of PC2 (%PC2) was correlated negatively with BBB breakdown in AD patients, unlike in natural aging or other reported disease conditions. The higher %PC2 in AD patients was also correlated with a lower Aβ42 plaque load and a lower Aβ42:Aβ40 ratio in the brain as determined by immunohistochemistry. Colocalization analysis of multicolor confocal immunofluorescence microscopy images suggests that AD patient with low %PC2 have higher BBB breakdown due to internalization of Aβ42 by the physiologically normal PC subset (PC1) and their concomitant cell death leading to more vessels without PCs and increased plaque load. On the contrary, it appears that PC2 can secrete cathepsin D to cleave and degrade Aβ built up outside of PC2 into more soluble forms, ultimately contributing to less BBB breakdown and reducing Aβ plaque load. Collectively our data shows functionally distinct mechanisms for PC1 and PC2 in high Aβ conditions, demonstrating the importance of correctly identifying these populations when investigating the contribution of neurovascular dysfunction to AD pathogenesis.

The integrated stress response (ISR) refers to signaling pathways initiated by stress-activated eIF2α kinases. Distinct eIF2α kinases respond to different stress signals, including amino acid deprivation and mitochondrial stress. Such stress-induced eIF2α phosphorylation attenuates general mRNA translation and, at the same time, stimulates the preferential translation of specific downstream factors to orchestrate an adaptive gene expression program. In recent years, there have been significant new advances in our understanding of ISR during metabolic stress adaptation. Here, I discuss those advances, reviewing among others the ISR activation mechanisms in response to amino acid deprivation and mitochondrial stress. In addition, I review how ISR regulates the amino acid metabolic pathways and how changes in the ISR impact the physiology and pathology of various disease models.

Biomolecular condensates organize biochemical processes at the subcellular level and can provide spatiotemporal regulation within a cell. Among these, ribonucleoprotein (RNP) granules are storage hubs for translationally repressed mRNA. Whether RNP granules can also activate translation and how this could be achieved remains unclear. Here, using single-molecule imaging, we demonstrate that the germ cell-determining RNP granules in Drosophila embryos are sites for active translation of nanos mRNA. Nanos translation occurs preferentially at the germ granule surface with the 3' UTR buried within the granule. Smaug, a cytosolic RNA-binding protein, represses nanos translation, which is relieved when Smaug is sequestered to the germ granule by the scaffold protein Oskar. Together, our findings uncover a molecular process by which RNP granules achieve localized protein synthesis through the compartmentalized loss of translational repression.

Glycolysis is a fundamental cellular process, yet its regulatory mechanisms remain incompletely understood. Here, we show that a subset of glucose transporter 1 (GLUT1/SLC2A1) co-endocytoses with platelet-derived growth factor (PDGF) receptor (PDGFR) upon PDGF-stimulation. Furthermore, multiple glycolytic enzymes localize to these endocytosed PDGFR/GLUT1-containing vesicles adjacent to mitochondria. Contrary to current models, which emphasize the importance of glucose transporters on the cell surface, we find that PDGF-stimulated glucose uptake depends on receptor/transporter endocytosis. Our results suggest that growth factors generate glucose-loaded endocytic vesicles that deliver glucose to the glycolytic machinery in proximity to mitochondria, and argue for a new layer of regulation for glycolytic control governed by cellular membrane dynamics.

Fanzor (Fz) is an ωRNA-guided endonuclease extensively found throughout the eukaryotic domain with unique gene editing potential. Here, we describe the structures of Fzs from three different organisms. We find that Fzs share a common ωRNA interaction interface, regardless of the length of the ωRNA, which varies considerably across species. The analysis also reveals Fz's mode of DNA recognition and unwinding capabilities as well as the presence of a non-canonical catalytic site. The structures demonstrate how protein conformations of Fz shift to allow the binding of double-stranded DNA to the active site within the R-loop. Mechanistically, examination of structures in different states shows that the conformation of the lid loop on the RuvC domain is controlled by the formation of the guide/DNA heteroduplex, regulating the activation of nuclease and DNA double-stranded displacement at the single cleavage site. Our findings clarify the mechanism of Fz, establishing a foundation for engineering efforts.

Muscle-specific kinase (MuSK) is essential for the formation, function, and preservation of neuromuscular synapses. Activation of MuSK by a MuSK agonist antibody may stabilize or improve the function of the neuromuscular junction (NMJ) in patients with disorders of the NMJ, such as congenital myasthenia (CM). Here, we generated and characterized ARGX-119, a first-in-class humanized agonist monoclonal antibody specific for MuSK, that is being developed for treatment of patients with neuromuscular diseases. We performed in vitro ligand-binding assays to show that ARGX-119 binds with high affinity to the Frizzled-like domain of human, nonhuman primate, rat, and mouse MuSK, without off-target binding, making it suitable for clinical development. Within the Fc region, ARGX-119 harbors L234A and L235A mutations to diminish potential immune-activating effector functions. Its mode of action is to activate MuSK, without interfering with its natural ligand neural Agrin, and cluster acetylcholine receptors in a dose-dependent manner, thereby stabilizing neuromuscular function. In a mouse model of DOK7 CM, ARGX-119 prevented early postnatal lethality and reversed disease relapse in adult Dok7 CM mice by restoring neuromuscular function and reducing muscle weakness and fatigability in a dose-dependent manner. Pharmacokinetic studies in nonhuman primates, rats, and mice revealed a nonlinear PK behavior of ARGX-119, indicative of target-mediated drug disposition and in vivo target engagement. On the basis of this proof-of-concept study, ARGX-119 has the potential to alleviate neuromuscular diseases hallmarked by impaired neuromuscular synaptic function, warranting further clinical development.