CK2 involvement in ESCRT-III complex phosphorylation.
The multivesicular body (MVB) sorting pathway is a mechanism for delivering transmembrane proteins into the lumen of the lysosome for degradation. ESCRT-III is the final complex in the pathway that assembles on endosomes and executes membrane scission of intraluminal vesicles. In addition, proteins of this complex are involved in other topologically similar processes such as cytokinesis, virus egress and autophagy. Here we show that protein kinase CK2α is involved in the phosphorylation of the ESCRT-III subunits CHMP3 and CHMP2B, as well as of VPS4B/SKD1, an ATPase that mediates ESCRT-III disassembly. This phosphorylation is observed both in vitro and in cells. While we do not observe recruitment of CK2α to endosomes, we demonstrate the localization of CK2α to midbodies during cytokinesis. Phosphomimetic and non-phosphorylatable mutants of ESCRT-III proteins can still bind endosomes and localize to midbodies, indicating that CK2α does not regulate ESCRT-III localization. Finally, we analyzed two cellular functions where CHMP3, CHMP2B and VPS4 are known to be involved, epidermal growth factor degradation and cytokinetic abscission. We demonstrate that the former is impaired by CK2α downregulation whereas the latter is not affected. Taken together, our results indicate that CK2α regulates the function of ESCRT-III proteins in MVB sorting.
Department of Biomedical Sciences, University of Padova, V.le G. Colombo 3, Padova, Italy. Electronic address: mauro.salvi@unipd.it.
Mauro
M
Salvi
Department of Biochemistry, Institute for Cancer Research, Oslo University Hospital, Montebello, Norway.
Camilla
C
Raiborg
Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO, USA.
Phyllis I
PI
Hanson
Department of Biochemistry, Institute for Cancer Research, Oslo University Hospital, Montebello, Norway.
Coen
C
Campsteijn
Department of Biochemistry, Institute for Cancer Research, Oslo University Hospital, Montebello, Norway.
Harald
H
Stenmark
Department of Biomedical Sciences, University of Padova, V.le G. Colombo 3, Padova, Italy; CNR Institute of Neurosciences, V.le G. Colombo 3, Padova, Italy; Venetian Institute for Molecular Medicine (VIMM), via Orus 2, 35129 Padova, Italy.
Lorenzo A
LA
Pinna
D000074183:ATPases Associated with Diverse Cellular Activities; D000251:Adenosine Triphosphatases / Q000032:analysis / Q000378:metabolism*; D047390:Casein Kinase II / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D015536:Down-Regulation; D056827:Endosomal Sorting Complexes Required for Transport / Q000032:analysis / Q000378:metabolism*; D011992:Endosomes / Q000378:metabolism; D004815:Epidermal Growth Factor / Q000378:metabolism; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D010766:Phosphorylation
C503812:CHMP2B protein, human; C498543:CHMP3 protein, human; D056827:Endosomal Sorting Complexes Required for Transport; D004815:Epidermal Growth Factor; D047390:Casein Kinase II; D000251:Adenosine Triphosphatases; D000074183:ATPases Associated with Diverse Cellular Activities; C490304:VPS4B protein, human
CHMP2B; CHMP3; ESCRT; Protein kinase CK2; VPS4