CSM News Electronic Edition Volume 4, number 8 March 4, 1995 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 at the URL "http://worms.cmsbio.nwu.edu/dicty.html" =========== Abstracts =========== Anchoring of an immunogenic Plasmodium falciparum circumsporozoite protein on the surface of Dictyostelium discoideum CHRISTOPHE D. REYMOND1, CAROLE BEGHDADI-RAIS2, MARIO ROGGERO2, ELIZABETH A. DUARTE2, CHANTAL DESPONDS2, MICHEL BERNARD2, DORINNE GROUX1, HUGUES MATILE3, CLAUDE BRON2, GIAMPIETRO CORRADIN2 AND NICOLAS J. FASEL2 1Institute of Histology and Embryology, University of Lausanne, Rue du Bugnon 9, 1005 Lausanne, Switzerland 2Institute of Biochemistry, University of Lausanne, ch. des Boveresses 155, 1066 Epalinges, Switzerland 3Hoffman La Roche Ltd, PRPI, Basel, Switzerland J. Biol. Chem., In Press ABSTRACT The circumsporozoite protein (CSP), a major antigen of Plasmodium falciparum, was expressed in the slime mould Dictyostelium discoideum. Fusion of the parasite protein to a leader peptide derived from Dictyostelium contact site A was essential for expression. The natural parasite surface antigen, however, was not detected at the slime mould cell surface as expected but retained intracellularly. Removal of the last 23 amino acids resulted in secretion of CSP suggesting that the C-terminal segment of the CSP, rather than an ectoplasmic domain, was responsible for retention. Cell surface expression was obtained when the CSP C-terminal segment was replaced by the Dictyostelium discoideum contact site A glycosyl-phosphatidylinositol (GPI) anchor signal sequence. Mice were immunised with Dictyostelium cells harbouring CSP at their surface. The raised antibodies recognised two different regions of the CSP. Anti-sporozoite titers of these sera were equivalent to anti-peptide titers detected by ELISA. Thus, cell surface targeting of antigens can be obtained in Dictyostelium, generating sporozoite like cells having potentials for vaccination, diagnostic tests or basic studies involving parasite cell surface proteins. ---------------------------------------------------------------------- Expression of cytochrome c oxidase during growth and development of Dictyostelium Dorianna Sandona', Stefano Gastaldello, Rosario Rizzuto and Roberto Bisson Dipartimento di Scienze Biomediche Sperimentali, Universita' di Padova, via Trieste 75, I-35121 Padova, Italy J. Biol. Chem. in press Abstract In the slime mold Dictyostelium discoideum, the subunit composition of cytochrome c oxidase depends on oxygen that inversely regulates the concentration of two alternative isoforms of the smallest enzyme subunit (Schiavo, G. and Bisson, R. (1989) J. Biol. Chem. 264, 7129-7134). In order to investigate their role in the Dictyostelium life cycle, the expression of the oxidase subunits was monitored during growth and development. The results obtained demonstrate that exponentially growing amoebae respond rapidly and precisely to hypoxia by switching the expression of the two isoforms and also by increasing the levels of the mRNAs of the differet oxidase subunits in a highly coordinated process. During normal development the "hypoxic" subunit is not synthesized, but its level of expression appears to parallel the sensitivity to oxygen of development, rising steeply below 10% oxygen when the differentiation program is virtually blocked. Under these conditions, the expression of the alternative subunit isoform is essentially oxygen-insensitive. These findings suggest that the physiological relevance of the subunit switching concerns primarily the vegetative phase of growth, possibly as part of a more general mechanism evolved in order to evade conditions that do not allow development. Taken together, the data obtained offer an intriguing example of the fine control exerted on the expression of a key respiratory enzyme in a strictly aerobic organism. --------------------------------------------------------------------- [End CSM-News, volume 4, number 8]