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A cryptic non-GPI-anchored cytosolic isoform of CD59 controls insulin exocytosis in pancreatic β-cells by interaction with SNARE proteins

Golec, Ewelina LU ; Rosberg, Rebecca LU ; Zhang, Enming LU ; Renström, Erik LU ; Blom, Anna M LU and King, Ben C LU (2019) In FASEB journal : official publication of the Federation of American Societies for Experimental Biology 33(11). p.12425-12434
Abstract

CD59 is a glycosylphosphatidylinositol (GPI)-anchored cell surface inhibitor of the complement membrane attack complex (MAC). We showed previously that CD59 is highly expressed in pancreatic islets but is down-regulated in rodent models of diabetes. CD59 knockdown but not enzymatic removal of cell surface CD59 led to a loss of glucose-stimulated insulin secretion (GSIS), suggesting that an intracellular pool of CD59 is required. In this current paper, we now report that non-GPI-anchored CD59 is present in the cytoplasm, colocalizes with exocytotic protein vesicle-associated membrane protein 2, and completely rescues GSIS in cells lacking endogenous CD59 expression. The involvement of cytosolic non-GPI-anchored CD59 in GSIS is supported... (More)

CD59 is a glycosylphosphatidylinositol (GPI)-anchored cell surface inhibitor of the complement membrane attack complex (MAC). We showed previously that CD59 is highly expressed in pancreatic islets but is down-regulated in rodent models of diabetes. CD59 knockdown but not enzymatic removal of cell surface CD59 led to a loss of glucose-stimulated insulin secretion (GSIS), suggesting that an intracellular pool of CD59 is required. In this current paper, we now report that non-GPI-anchored CD59 is present in the cytoplasm, colocalizes with exocytotic protein vesicle-associated membrane protein 2, and completely rescues GSIS in cells lacking endogenous CD59 expression. The involvement of cytosolic non-GPI-anchored CD59 in GSIS is supported in phosphatidylinositol glycan class A knockout GPI anchor-deficient β-cells, in which GSIS is still CD59 dependent. Furthermore, site-directed mutagenesis demonstrated different structural requirements of CD59 for its 2 functions, MAC inhibition and GSIS. Our results suggest that CD59 is retrotranslocated from the endoplasmic reticulum to the cytosol, a process mediated by recognition of trimmed N-linked oligosaccharides, supported by the partial glycosylation of non-GPI-anchored cytosolic CD59 as well as the failure of N-linked glycosylation site mutant CD59 to reach the cytosol or rescue GSIS. This study thus proposes the previously undescribed existence of non-GPI-anchored cytosolic CD59, which is required for insulin secretion.-Golec, E., Rosberg, R., Zhang, E., Renström, E., Blom, A. M., King, B. C. A cryptic non-GPI-anchored cytosolic isoform of CD59 controls insulin exocytosis in pancreatic β-cells by interaction with SNARE proteins.

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author
; ; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Animals, CD59 Antigens/genetics, CHO Cells, Cricetulus, Cytosol/metabolism, Exocytosis, Insulin/genetics, Insulin Secretion, Insulin-Secreting Cells/cytology, Oligosaccharides/genetics, Rats, SNARE Proteins/genetics
in
FASEB journal : official publication of the Federation of American Societies for Experimental Biology
volume
33
issue
11
pages
10 pages
publisher
The Federation of American Societies for Experimental Biology
external identifiers
  • scopus:85074377944
  • pmid:31412214
ISSN
1530-6860
DOI
10.1096/fj.201901007R
language
English
LU publication?
yes
id
86917bb5-a6bd-48fb-bb00-5268b4ae6eff
date added to LUP
2021-03-09 21:57:58
date last changed
2021-06-08 03:08:48
@article{86917bb5-a6bd-48fb-bb00-5268b4ae6eff,
  abstract     = {<p>CD59 is a glycosylphosphatidylinositol (GPI)-anchored cell surface inhibitor of the complement membrane attack complex (MAC). We showed previously that CD59 is highly expressed in pancreatic islets but is down-regulated in rodent models of diabetes. CD59 knockdown but not enzymatic removal of cell surface CD59 led to a loss of glucose-stimulated insulin secretion (GSIS), suggesting that an intracellular pool of CD59 is required. In this current paper, we now report that non-GPI-anchored CD59 is present in the cytoplasm, colocalizes with exocytotic protein vesicle-associated membrane protein 2, and completely rescues GSIS in cells lacking endogenous CD59 expression. The involvement of cytosolic non-GPI-anchored CD59 in GSIS is supported in phosphatidylinositol glycan class A knockout GPI anchor-deficient β-cells, in which GSIS is still CD59 dependent. Furthermore, site-directed mutagenesis demonstrated different structural requirements of CD59 for its 2 functions, MAC inhibition and GSIS. Our results suggest that CD59 is retrotranslocated from the endoplasmic reticulum to the cytosol, a process mediated by recognition of trimmed N-linked oligosaccharides, supported by the partial glycosylation of non-GPI-anchored cytosolic CD59 as well as the failure of N-linked glycosylation site mutant CD59 to reach the cytosol or rescue GSIS. This study thus proposes the previously undescribed existence of non-GPI-anchored cytosolic CD59, which is required for insulin secretion.-Golec, E., Rosberg, R., Zhang, E., Renström, E., Blom, A. M., King, B. C. A cryptic non-GPI-anchored cytosolic isoform of CD59 controls insulin exocytosis in pancreatic β-cells by interaction with SNARE proteins.</p>},
  author       = {Golec, Ewelina and Rosberg, Rebecca and Zhang, Enming and Renström, Erik and Blom, Anna M and King, Ben C},
  issn         = {1530-6860},
  language     = {eng},
  number       = {11},
  pages        = {12425--12434},
  publisher    = {The Federation of American Societies for Experimental Biology},
  series       = {FASEB journal : official publication of the Federation of American Societies for Experimental Biology},
  title        = {A cryptic non-GPI-anchored cytosolic isoform of CD59 controls insulin exocytosis in pancreatic β-cells by interaction with SNARE proteins},
  url          = {http://dx.doi.org/10.1096/fj.201901007R},
  doi          = {10.1096/fj.201901007R},
  volume       = {33},
  year         = {2019},
}