Eukaryotic G protein coupled receptors (GPCRs) control physiological processes, as diverse as, homeostasis, vision, and chemotactic movement. Migratory cells, like mammalian leukocytes and Dictyostelium discoideum, utilize GPCR signaling to regulate MAPK/ERK, PI3K, TORC2/AKT, adenylyl cyclase, and actin polymerization, which collectively direct chemotaxis. Upon ligand binding, mammalian GPCRs are often phosphorylated at cytoplasmic residues, uncoupling G protein pathways, but activating others. In developing Dictyostelium, secreted cAMP serves as a chemoattractant, with extracellular cAMP propagated as oscillating waves to ensure directional migratory signals. The cAMP oscillations derive from a transient excitatory response of adenylyl cyclase, which then rapidly adapts. Most chemotactic responses are similarly transient when cAMP is presented persistently. We have studied chemotactic signaling in Dictyostelium that express non-phosphorylatable cAMP receptors and provide evidence that receptor phosphorylation is required for effective polarization and chemotaxis of Dictyostelium to cAMP. We also show that these cells are unable to regulate adaptation of adenylyl cyclase, which disrupts long-range oscillatory cAMP wave production and cytoskeletal actin response. These data indicate that chemoattractant receptor phosphorylation is required to co-regulate essential pathways for Dictyostelium and perhaps other migratory cells. Mutations in two presenilin proteins cause Familial Alzheimer's disease. These proteins function in both a proteolytic-dependent activity within the gamma-secretase complex and in a scaffold-related function. Analysing the cellular role of these proteins has been complex due to embryonic lethality following deletion of both genes. We had previously shown that in the simple biomedical model, Dictyostelium discoideum, these proteins have a developmental role. Here we show that the developmental role can be rescued by the human presenilin 1 protein, controlling terminal differentiation in multiple cell types. We also show that morphological development can be rescued with the human presenilin protein carrying a single D/A catalytic mutation, suggesting a non-proteolytic role for presenilin proteins in development. The conserved function of presenilin proteins in these distantly related species is also shown in that the D. discoideum proteins show proteolytic (Notch cleavage) activity in mammalian (mouse blastocyst)-derived cells. We further show that elevated cyclic AMP (cAMP) levels and enhanced stimulation-induced calcium release result from presenilin loss in D. discoideum, suggesting dysregulation of intracellular signalling pathways involving these second messengers in this model. Our data therefore suggests ancient roles for presenilin proteins in regulating intracellular signalling and development and provides a novel, model system for the analysis of human presenilin function. Perilipin family proteins (Plins) coat the surface of intracellular neutral lipid storage droplets in various cell types. Studies across diverse species demonstrate that Plins regulate lipid storage metabolism through recruitment of lipases and other regulatory proteins to lipid droplet surfaces. Mammalian genomes encode 5 distinct Plin gene members and additional protein forms derive from specific mRNA splice variants. However, it is not known if the different Plins have distinct functional properties. Using biochemical, cellular imaging, and flow cytometric analyses, we now show that within individual cells of various types, the different Plin proteins preferentially sequester to separate pools of lipid storage droplets. By examining ectopically expressed GFP fusions and all endogenous Plin protein forms, we demonstrate that different Plins sequester to lipid droplets, comprised distinctly of either triacylcerides or of cholesterol esters. Further, Plins with strong association preferences to TAG (or CE) droplets can re-direct the relative intracellular TAG/CE balance toward the targeted lipid. Our data suggest diversity of Plin function, alter previous assumptions about shared collective actions of the Plins, and indicate that each Plin can have separate and unique functions. The TOR protein kinase functions in two distinct complexes, TOR Complexes 1 (TORC1) and 2 (TORC2). TORC1 is required for growth in response to growth factors, nutrients, and cellular energy state;TORC2 is documented to regulate AKT signaling, which can modulate cytoskeletal polarization. In its ecological niche, Dictyostelium engulf bacteria and yeast for nutrient capture. Despite the essential role of TORC1 in control of cellular growth, we show that nutrient particle capture, phagocytosis, in Dictyostelium is independent of TORC1 mediated nutrient sensing and growth regulation. However, loss of Dictyostelium TORC2 components Rictor/Pia, SIN1/RIP3, and Lst8 promotes nutrient particle uptake;inactivation of TORC2 leads to increased efficiency and speed of phagocytosis. In contrast to phagocytosis, we show that macropinocytosis, an AKT-dependent process for cellular uptake of fluid phase nutrients, is not regulated by either TOR complex. The integrated and balanced regulations of TORC1 and TORC2 may be critical in Dictyostelium to coordinate growth and energy needs with other essential TOR-regulated processes. The CHD (Chromodomain-Helicase-DNA binding) family is one of the major ATP-dependent, chromatin remodeling proteins that regulate nucleosome positioning and gene expression in eukaryotes. Mammalian CHD proteins group into three subfamilies and several human diseases are associated with impaired CHD function. Here, we identify three CHDs (ChdA, ChdB, and ChdC) in Dictyostelium discoideum that are expressed with unique developmental patterns. Null mutants for each have distinct, non-redundant phenotypes, indicating functional specificity. ChdC clusters with members of CHD subfamily 3 that includes mammalian CHD7. Mutations in CHD7 are associated with the human CHARGE syndrome, characterized by multiple congenetical developmental defects, and in Dictyostelium, chdC-nulls similarly have severe and diverse developmental phenotypes. To understand the mechanistic function of ChdC and related CHDs, we compared genome-wide nucleosomal maps of wild-type (WT) cells during growth and development and those of chdC-nulls. We show that nucleosome-spacing is altered in a subset of genes in chdC-nulls and that gene-specific transcriptional profiling changes correlate statistically with these unique nucleosomal patterning differences and phenotypic defects. This study provides novel mechanistic insight into the action of a class of CHDs in chromatin organization and may serve as a basis to better understand certain human genetic defects.
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