Dicty News Electronic Edition Volume 16, number 10 May 12, 2001 Please submit abstracts of your papers as soon as they have been accepted for publication by sending them to dicty@northwestern.edu. Back issues of Dicty-News, the Dicty Reference database and other useful information is available at DictyBase--http://dictybase.org. ============= Dicty 2001 ============= DICTYOSTELIUM 2001 The deadline for abstracts to this year's meeting is soon approaching. Please send your abstracts as soon as possible. To encourage prompt registrations the cost of the meeting was initially set slightly higher for those who register after today. However, we have decided to wave the extra cost for those who register by May 21. However, we request that you register NOW. Abstract dead will also be extended to May 21. In addition, we need to institute a "drop-dead" deadline of May 28. No registrations or abstracts will be accepted after that date. We encourage all those with an interest in the organism to attend. This meeting will maintain its strong emphasis on developmental biology and genomics but will also have an increased emphasis on cell biology since this aspect of the field is growing at an appreciable rate and the organism is now at the forefront of many aspects of this field. Please register as soon as possible. Best regards, Bill and Rick ============== Abstracts ============== Regulated protein degradation controls PKA function and cell-type differentiation in Dictyostelium Sudhasri Mohanty, Susan Lee, Nagendra Yadava, Marian J. Dealy, Randall S. Johnson, and Richard A. Firtel Genes and Development, in press SUMMARY Cullins function as scaffolds that, along with F-box/WD40-repeat-containing proteins, mediate the ubiquitination of proteins to target them for degradation by the proteasome. We have identified a cullin CulA that is required at several stages during Dictyostelium development. culA null cells are defective in inducing cell-type-specific gene expression and exhibit defects during aggregation, including reduced chemotaxis. PKA is an important regulator of Dictyostelium development. The levels of intracellular cAMP and PKA activity are controlled by the rate of synthesis of cAMP and its degradation by the cAMP-specific phosphodiesterase RegA. We demonstrate that overexpression of the PKA catalytic subunit (PKAcat) rescues many of the culA null defects and those of cells lacking FbxA/ChtA, a previously described F-box/WD40-repeat-containing protein, suggesting CulA and FbxA proteins are involved in regulating PKA function. Whereas RegA protein levels drop as the multicellular organism forms in the wild- type strain, they remain high in culA null and fbxA null cells. Although PKA can suppress the culA and fbxA null developmental phenotypes, it does not suppress the altered RegA degradation, suggesting that PKA lies downstream of RegA, CulA, and FbxA. Finally, we demonstrate that CulA, FbxA, and RegA are found in a complex in vivo and formation of this complex is dependent on the MAP kinase ERK2, which is also required for PKA function. We propose that CulA and FbxA regulate multicellular development by targeting RegA for degradation via a pathway that requires ERK2 function, leading to an increase in cAMP and PKA activity. ---------------------------------------------------------------------------- - Signaling at zero G: G-protein-independent functions for 7-TM receptors Joseph A. Brzostowski and Alan R. Kimmel* Laboratory of Cellular and Developmental Biology, NIDDK (MMDS; Bldg 6/B1-22), National Institutes of Health, Bethesda, MD 20892-2715, USA. *e-mail: ark1@helix.nih.gov Trends in Biochemical Sciences Vol.26 No.5 May 2001 Eukaryotic cells, whether free-living, single-celled microbes or components of complex metazoa, can sense environmental cues through specialized seven-transmembrane (7-TM) receptors (also called heptahelical or G-protein-coupled receptors). 7-TM receptors detect 'inputs' such as light, peptide hormones, neurotransmitters, pheromones, odorants, morphogens and chemoattractants, linking extracellular stimuli to intracellular signaling networks via heterotrimeric G proteins. Recently, this obligatory paradigm has been challenged. A growing body of evidence indicates that 7-TM receptors can also transmit extracellular signals through mechanisms that function independently of G-protein coupling. This review discusses pathways and protein interactions for 7-TM receptors signaling 'at zero G' in Dictyostelium and mammalian cells. ---------------------------------------------------------------------------- [End Dicty News, volume 16, number 10]