Copine A regulates the size and exocytosis of contractile vacuoles and postlysosomes in Dictyostelium

Elise M. Wight, Amber D. Ide, Cynthia K. Damer

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

Copines are a family of cytosolic proteins that associate with membranes in a calcium-dependent manner and are found in many eukaryotic organisms. Dictyostelium discoideum has six copine genes (cpnA-cpnF), and cells lacking cpnA(cpnA) have defects in cytokinesis, chemotaxis, adhesion, and development. CpnA has also been shown to associate with the plasma membrane, contractile vacuoles (CV), and organelles of the endolysosomal pathway. Here, we use cpnA cells to investigate the role of CpnA in CV function and endocytosis. When placed in water, cpnA cells made abnormally large CVs that took longer to expel. Visualization of CVs with the marker protein GFP-dajumin indicated that cpnA cells had fewer CVs that sometimes refilled before complete emptying. In endocytosis assays, cpnA cells took up small fluorescent beads by macropinocytosis at rates similar to parental cells. However, cpnA cells reached a plateau sooner than parental cells and had less fluorescence at later time points. p80 antibody labeling of postlysosomes (PL) indicated that there were fewer and smaller PLs in cpnA cells. In dextran pulse-chase experiments, the number of PLs peaked earlier in cpnA cells, and the PLs did not become as large and disappeared sooner as compared to parental cells. PLs in cpnA cells were also shown to have more actin coats, suggesting CpnA may play a role in actin filament disassembly on PL membranes. Overall, these results indicate that CpnA is involved in the regulation of CV size and expulsion, and the maturation, size, and exocytosis of PLs.

Original languageEnglish
Pages (from-to)979-994
Number of pages16
JournalFEBS Open Bio
Volume10
Issue number6
DOIs
StatePublished - Jun 1 2020

Keywords

  • Dictyostelium
  • contractile vacuole
  • copine
  • endocytosis
  • exocytosis
  • postlysosome

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