CSM News Electronic Edition Volume 2, number 18 May 21, 1994 Please submit abstracts of your papers as soon as they have been accepted for publication by sending them to CSM-News@worms.cmsbio.nwu.edu. Back issues of CSM-News, the CSM Reference database and other useful information is available by anonymous ftp from worms.cmsbio.nwu.edu [165.124.233.50], via Gopher at the same address, or by World Wide Web through www.nwu.edu. ----------------------------------------------------------------------- NOTE: The IP number for the computer that maintains the Dicty archive has changed from 129.105.233.50 to 165.124.233.50. For those of you who use the name "worms.cmsbio.nwu.edu" this change should not affect you. However, if you have been using the actual numerical address it will need to be changed (preferably to the name). ========== Abstracts ========== The PsB Glycoprotein Complex Is Secreted as a Preassembled Precursor of the Spore Coat in Dictyostelium discoideum. Ned Watson, Vince McGuire and Stephen Alexander Division of Biological Sciences University of Missouri Columbia, MO 65211 J. Cell Science, in press SUMMARY The PsB glycoprotein in Dictyostelium discoideum is one of a diverse group of developmentally regulated, prespore cell specific proteins, which contain a common O-linked oligosaccharide. This post-translational modification is dependent on the wild-type modB allele. The PsB protein exists as part of a multiprotein complex of six different proteins, which have different post-translational modifications and are held together by both covalent and non-covalent interactions (Watson et al., J. Biol. Chem., 268, 22634-22641, 1993). In this study we have used microscopic and biochemical analyses to examine the cellular localization and function of the PsB complex during development. We found that the PsB complex first accumulates in prespore vesicles in slug cells and is secreted later during culmination and becomes localized to both the extracellular matrix of the apical spore mass of mature fruiting bodies and to the inner layer of the spore coat. The PsB associated with the spore coat is covalently bound by disulfide bridges. The PsB protein always exists in a multiprotein complex, but the composition of the PsB complex changes during secretion and spore maturation. Some of the other PsB complex proteins have been identified as spore coat proteins. These data demonstrate that some of the proteins which form the spore coat exist as a preassembled precursor complex. The PsB complex is secreted in a developmentally regulated manner during the process of spore differentiation, at which time proteins of the complex, as well as additional spore coat proteins, become covalently associated in at least two forms of extracellular matrix: the interspore matrix and the spore coat. These and other studies show that proteins with modB dependent O-linked oligosaccharides are involved in a wide variety of processes underlying morphogenesis in this organism. These developmental processes are the direct result of cellular mechanisms regulating protein targeting, assembly and secretion, and the assembly of specific extracellular matrices. --------------------------------------------------------------------- [End CSM-News, volume 2, number 18]