dictyNews
Electronic Edition
Volume 46, number 4
February 7, 2020
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Abstracts
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Calmodulin and Calmodulin Binding Proteins in Dictyostelium: A Primer
Danton H. O’Day1,2, Ryan J. Taylor3 and Michael A. Myre3
1Cell and Systems Biology, University of Toronto, Toronto, Ontario,
Canada M5S 3G5
2Department of Biology, University of Toronto Mississauga, Mississauga,
Ontario, Canada L5L 1C6
3 Department of Biological Sciences, Kennedy College of Sciences,
University of Massachusetts Lowell, Lowell, MA 01854, USA
*Correspondence: [log in to unmask]
International Journal of Molecular Sciences, in press
Special issue on “Calmodulin Function in Health and Disease”
Antonio Villalobo and Martin W. Berchtold, Guest Editors
Dictyostelium discoideum is gaining increasing attention as a model
organism for the study of calcium binding and calmodulin function in
basic biological events as well as human diseases. After a short overview
of calcium-binding proteins, the structure of Dictyostelium calmodulin and
the conformational changes effected by calcium ion binding to its four
EF hands are compared to its human counterpart, emphasizing the highly
conserved nature of this central regulatory protein. The calcium-dependent
and -independent motifs involved in calmodulin binding to target proteins
are discussed with examples of the diversity of calmodulin binding proteins
that have been studied in this amoebozoan. The methods used to identify
and characterize calmodulin binding proteins is covered followed by the
ways Dictyostelium is currently being used as a system to study several
neurodegenerative diseases and how it could serve as a model for studying
calmodulinopathies such as those associated with specific types of heart
arrythmia. Because of its rapid developmental cycles, its genetic tractability,
and a richly endowed stock center, Dictyostelium is in a position to
become a leader in the field of calmodulin research.
submitted by: Danton O’Day [[log in to unmask]]
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The proppin Bcas3 and its interactor KinkyA localize to the early phagophore
and regulate autophagy
Yoko Yamada1,2 and Pauline Schaap1*
1School of Life Sciences, University of Dundee, Dundee, DD15EH, UK
2Department of Biology, Faculty of Science, Toho University, Funabashi,
Chiba 274-8510, Japan
Autophagy, in press
To resolve the signaling mechanisms that mediate the starvation-induced
processes of Dictyostelium sporulation and encystation, we performed
insertional mutagenesis on cells harboring an mRFP-tagged spore gene.
We isolated a mutant in kinkyA (knkA), a gene without known function, which
formed fruiting bodies with a kinked stalk and lacking viable spores.
Immunoprecipitation of lysates of KnkA-YFP-transformed knkA- cells yielded
a mammalian BCAS3 homolog as a KnkA interactor. bcas3- phenocopied
knkA- and Bcas3 colocalized with KnkA to puncta. Bcas3 shares sequence
similarity with proppins (beta-propellors that bind phosphoinositides).
Mutation of 2 Bcas3 residues that are essential for PtdIns3P binding in
proppins prevented Bcas3 binding to PtdIns3P as well as punctate Bcas3 and
KnkA localization. KnkA puncta also colocalized with small but not large
vesicles that contain the autophagy protein Atg8 and were contiguous with the
endoplasmic reticulum. knkA- and bcas3- cells showed a pronounced decrease
of RFP-GFP-Atg8 in neutral early autophagosomes, indicating that KnkA and
Bcas3 are required for macroautophagy/autophagy. Knockouts in atg7, atg5 or
atg9 substantiated this finding by showing similar sporulation defects as knk-
and bcas3-. Defective Dictyostelium sporulation is evidently a useful diagnostic
tool for the discovery of novel autophagy genes.
submitted by: Pauline Schaap [[log in to unmask]]
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[End dictyNews, volume 46, number 4]
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