Activity

GABAA receptors (GABAARs) mediate inhibitory neurotransmission in the mammalian brain. Recently, numerous GABAAR static structures have been published, but the molecular mechanisms of receptor activation remain elusive. Adavivint mouse Loop G is a rigid β-strand belonging to an extensive β-sheet that spans the regions involved in GABA binding and the interdomain interface which is important in receptor gating. It has been reported that loop G participates in ligand binding and gating of GABAARs, however, it remains unclear which specific gating transitions are controlled by this loop. Analysis of macroscopic responses revealed that mutation at the α1F45 residue (loop G midpoint) resulted in slower macroscopic desensitization and accelerated deactivation. Single-channel analysis revealed that these mutations also affected open and closed times distributions and reduced open probability. Kinetic modeling demonstrated that mutations affected primarily channel opening/closing and ligand binding with a minor effect on preactivation. Thus, α1F45 residue, in spite of its localization close to binding site, affects late gating transitions. In silico structural analysis suggested an important role of α1F45 residue in loop G stability and rigidity as well as in general structure of the binding site. We propose that the rigid β-sheet comprising loop G is well suited for long range communication within GABAAR but this mechanism becomes impaired when α1F45 is mutated. In conclusion, we demonstrate that loop G is crucial in controlling both binding and gating of GABAARs. These data shed new light on GABAAR activation mechanism and may also be helpful in designing clinically relevant modulators. Chronic kidney disease, commonly fostering non-renal complications, themselves more life-threatening than renal pathology, remain enigmatic. Despite more than a century of intense research, therapeutic options to halt or reverse renal disease are rather limited. Recently, similarity between manifestations of progressive chronic kidney disease and aging kidney has attracted investigative attention that revealed senescent cells, secreting proinflammatory and profibrotic mediators, in all renal compartments even at young age in patients with kidney maladies. The overlapping features of these categories have been noticed previously and are briefly summarized herein. I propose two hypothetical scenarios for interactive association of kidney diseases and cell senescence, both culminating in progressive deterioration of renal function. Persistence of senescent cells is considered as a critical contributor to this association and the mechanisms explaining persistence, such as activation of cell cycle regulators, anti-apoptotic stimuli, metabolic aberrations, and their interactions are discussed. The mutual encroachment of underlying kidney disease and cell senescence bring about the conclusion that both entities merge along the natural history of the disease. This putative interpretation of vicarious relation between cell senescence and chronic kidney disease may expand the arsenal of pharmacotherapy to include the judicious use of senotherapeutics in the management of renal disease. Osteomyelitis is an inflammation of the bone and bone marrow that is most commonly caused by a Staphylococcus aureus infection. Much of our understanding of the underlying pathophysiology of osteomyelitis, from the perspective of both host and pathogen, has been revised in recent years, with notable discoveries including the role played by osteocytes in the recruitment of immune cells, the invasion and persistence of S. aureus in sub-micron channels of cortical bone, and the diagnostic role of polymorphonuclear cells in implant associated osteomyelitis. Advanced in vitro cell culture models such as ex vivo culture models or organoids have also been developed over the past decade, and have become widespread in many fields, including infectious diseases. These models better mimic the in vivo environment, allow the use of human cells, and can reduce our reliance on animals in osteomyelitis research. In this review, we provide an overview of the main pathological concepts in osteomyelitis, with a focus on the new discoveries in recent years. Furthermore, we outline the value of modern in vitro cell culture techniques, with a focus on their current application to infectious diseases and osteomyelitis in particular. Lysosomal acid ceramidase (Ac) has been shown to be critical for ceramide hydrolysis and regulation of lysosome function and cellular homeostasis. In the present study, we generated a knockout mouse line (Asah1fl/fl/PodoCre) with a podocyte-specific deletion of the alpha subunit (main catalytic subunit) of Ac. Although no significant morphologic changes in glomeruli were observed in these mice under light microscope, severe proteinuria and albuminuria were found in these podocyte-specific KO mice compared to control genotype littermates. Transmission electron microscopic analysis showed that podocytes of the KO mice had distinctive foot process effacement and microvillus formation. These functional and morphologic changes indicate the development of nephrotic syndrome in mice bearing the Asah1 podocyte-specific gene deletion. Ceramide accumulation determined by LC-MS/MS was demonstrated in isolated glomeruli of Asah1fl/fl/PodoCre mice compared to their littermates. By cross breeding Asah1fl/fl/PodoCre mice with Smpd1-/- mice, we also produced a double KO strain, Smpd1-/-/Asah1fl/fl/PodoCre, that also lacks Smpd1, the acid sphingomyelinase that hydrolyzes sphingomyelin to ceramide. These mice exhibited significantly lower levels of glomerular ceramide with decreased podocyte injury compared with Asah1fl/fl/PodoCre mice. These results strongly suggest that lysosomal Ac in podocytes is essential for the maintenance of the structural and functional integrity of podocytes. The cyclin dependent kinase inhibitor 2A (CDKN2A)/alternate reading frame (ARF) locus consists of two overlapping tumor suppressor genes, p16INK4a and p14ARF (p19Arf in mice), encoding two unrelated proteins in alternative reading frames. Previous reports suggest that p16INK4a and p14ARF alterations independently exhibit differential roles, and p16INK4a is more closely associated with a poor prognosis in oral cancer. However, the role of p16INK4a -specific loss in oral squamous cell carcinogenesis remains unclear. We assessed chemical carcinogen 4-nitroquinoline 1-oxide (4NQO)-induced multistep oral squamous cell carcinogenesis in mice carrying p16INK4a -specific loss with retention of the p19ARF gene (p16 INK4a -/-). 4NQO-treated p16-/- mice exhibited a higher incidence and multiplicity of oral squamous cell carcinoma (OSCC) development relative to 4NQO-treated wild-type mice. 4NQO-treated p16 INK4a -/- OSCC cells exhibited higher proliferation and upregulation of Arf, transcription factor E2f1, tumor protein p63 (tp63), and oncogenic ΔNp63, an isoform p63, compared with observations in 4NQO-treated wild-type OSCC cells.