G protein function during biomembrane fusion in Dictyostelium: presence and importance of a G alpha s subunit during fertilization and phagocytosis.
Previous work has shown that GTPase function is essential for fertilization and cannibalistic phagocytosis during the sexual development of Dictyostelium discoideum. In this work, the importance of heterotrimeric G proteins during these events was established further using aluminum fluoride which inhibited both fertilization and cannibalistic phagocytosis, as well as the phagocytosis of bacteria by vegetative amoebae. Using distinct immune sera directed against the amino terminus and the carboxy terminus of mammalian G alpha s, we have provided unique evidence for a G alpha s subunit of approximately 55 kDa in D. discoideum (referred to as dG alpha s). Furthermore, this protein localizes to the membranes of fusing cells as well as to both vegetative and zygote giant cells, indicating that it might function during fertilization as well as during both vegetative (i.e., bacterial) and cannibalistic (i.e., amoebal) phagocytosis. During its down-regulation in nonphagocytic cells new isozymes of dG alpha s appear, suggesting that it may be posttranslationally modified. Having identified a putitive G alpha s homologue, this work has set the stage for further investigations into its function in Dictyostelium.
Browning
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DD
Department of Zoology, University of Toronto, Mississauga, Ontario, Canada.
O'Day
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DH
D017607:Aluminum Compounds / Q000494:pharmacology; D000818:Animals; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology; D004023:Dictyostelium / Q000502:physiology*; D005459:Fluorides / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000737:chemistry* / Q000502:physiology; D010587:Phagocytosis
D017607:Aluminum Compounds; D019204:GTP-Binding Proteins; D005459:Fluorides; C032311:aluminum fluoride