Raf kinase activation of adenylyl cyclases: isoform-selective regulation

ABSTRACT Adenylyl cyclases (AC), a family of enzymes that catalyze the synthesis of cyclic AMP, are critical regulators of cellular functions. The activity of adenylyl cyclase is stimulated by a range of hormone receptors, primarily via interactions with G-proteins; however, recently we identified an alternate mechanism by which growth factors sensitize adenylyl cyclase activation. We suggested that this mechanism might involve a Raf kinasemediated serine phosphorylation of adenylyl cyclase. However, the direct involvement of a specific form of Raf kinase is yet to be demonstrated. Furthermore, whether this mechanism is generalized to other isoforms of adenylyl cyclase is unknown. In human embryonic kidney 293 cells, we now demonstrate that in reconstitution studies, c-Raf kinase can mediate phosphorylation of AC VI. Furthermore, AC VI coimmunoprecipitates with c-Raf. Raf kinase-dependent regulation of adenylyl cyclase VI is dependent on the integrity of Ser750 in the fourth intracellular loop of the enzyme and Ser603/Ser608 in the C1b region of the molecule. To examine how generalized this effect is, we studied representative isoforms of the major subfamilies of adenylyl cyclase viz., AC I, AC II, and AC V. Raf kinase-dependent sensitization/ phosphorylation of adenylyl cyclases is common to AC VI, AC V, and AC II isoforms but not AC I. In aggregate, these studies indicate that Raf kinase associates with adenylyl cyclases. Furthermore, Raf kinase regulation of adenylyl cyclase is isoform-selective. These functional interactions (as well as the physical association) between adenylyl cyclases and Raf kinases suggest an important but previously unrecognized interaction between these two key regulatory enzymes

Non-linear magnons and exchange Hamiltonians of delafossite proximate quantum spin liquids

Quantum spin liquids (QSL) are theoretical states of matter with long-range entanglement and exotic quasiparticles. However, they generally elude quantitative theory, rendering their underlying phases mysterious and hampering efforts to identify experimental QSL states. Here we study triangular lattice resonating valence bond QSL candidate materials KYbSe$_2$ and NaYbSe$_2$. We measure the magnon modes in their 1/3 plateau phase, where quantitative theory is tractable, using inelastic neutron scattering and fit them using nonlinear spin wave theory. We also fit the KYbSe$_2$ heat capacity using high temperature series expansion. Both KYbSe$_2$ fits yield the same magnetic Hamiltonian to within uncertainty, confirming previous estimates and showing the Heisenberg $J_2/J_1$ to be an accurate model for these materials. Most importantly, comparing KYbSe$_2$ and NaYbSe$_2$ shows that smaller $A$-site Na$^+$ ion has a larger $J_2/J_1$ ratio. However, hydrostatic pressure applied to KYbSe$_2$ increases the ordering temperature (a result consistent with density functional theory calculations), indicating that pressure decreases $J_2/J_1$. These results show how periodic table and hydrostatic pressure can tune the $A$YbSe$_2$ materials in a controlled way.Comment: 7 pages, 7 figures; 4 pages and 7 additional figures of supplemental informatio

Alternative splicing of exon 10 in the tau gene as a target for treatment of tauopathies

Tau aggregation is one of the major features in Alzheimer's disease and in several other tauopathies, including frontotemporal dementia with Parkinsonism linked to chromosome 17 (FTDP-17), and progressive supranuclear palsy (PSP). More than 35 mutations in the tau gene have been identified from FTDP-17 patients. A group of these mutations alters splicing of exon 10, resulting in an increase in exon 10 inclusion into tau mRNA. Abnormal splicing with inclusion of exon 10 into tau mRNA has also been observed in PSP and AD patients. These results indicate that abnormal splicing of exon 10, leading to the production of tau with exon 10, is probably one of the mechanisms by which tau accumulates and aggregates in tauopathic brains. Therefore, modulation of exon 10 splicing in the tau gene could potentially be targeted to prevent tauopathies. To identify small molecules or compounds that could potentially be developed into drugs to treat tauopathies, we established a cell-based high-throughput screening assay. In this review, we will discuss how realistic, specific biological molecules can be found to regulate exon 10 splicing in the tau gene for potential treatment of tauopathies

A multimodal cell census and atlas of the mammalian primary motor cortex

ABSTRACT We report the generation of a multimodal cell census and atlas of the mammalian primary motor cortex (MOp or M1) as the initial product of the BRAIN Initiative Cell Census Network (BICCN). This was achieved by coordinated large-scale analyses of single-cell transcriptomes, chromatin accessibility, DNA methylomes, spatially resolved single-cell transcriptomes, morphological and electrophysiological properties, and cellular resolution input-output mapping, integrated through cross-modal computational analysis. Together, our results advance the collective knowledge and understanding of brain cell type organization: First, our study reveals a unified molecular genetic landscape of cortical cell types that congruently integrates their transcriptome, open chromatin and DNA methylation maps. Second, cross-species analysis achieves a unified taxonomy of transcriptomic types and their hierarchical organization that are conserved from mouse to marmoset and human. Third, cross-modal analysis provides compelling evidence for the epigenomic, transcriptomic, and gene regulatory basis of neuronal phenotypes such as their physiological and anatomical properties, demonstrating the biological validity and genomic underpinning of neuron types and subtypes. Fourth, in situ single-cell transcriptomics provides a spatially-resolved cell type atlas of the motor cortex. Fifth, integrated transcriptomic, epigenomic and anatomical analyses reveal the correspondence between neural circuits and transcriptomic cell types. We further present an extensive genetic toolset for targeting and fate mapping glutamatergic projection neuron types toward linking their developmental trajectory to their circuit function. Together, our results establish a unified and mechanistic framework of neuronal cell type organization that integrates multi-layered molecular genetic and spatial information with multi-faceted phenotypic properties