ER-Targeted Beclin 1 Supports Autophagosome Biogenesis in the Absence of ULK1 and ULK2 Kinases

Tahira Anwar, Xiaonan Liu, Taina Suntio, Annika Marjamäki, Joanna Biazik, Edmond Y. W. Chan, Markku Varjosalo, Eeva-Liisa Eskelinen

Research output: Contribution to journalArticleScientificpeer-review

Abstract

Autophagy transports cytoplasmic material and organelles to lysosomes for degradation and recycling. Beclin 1 forms a complex with several other autophagy proteins and functions in the initiation phase of autophagy, but the exact role of Beclin 1 subcellular localization in autophagy initiation is still unclear. In order to elucidate the role of Beclin 1 localization in autophagosome biogenesis, we generated constructs that target Beclin 1 to the endoplasmic reticulum (ER) or mitochondria. Our results confirmed the proper organelle-specific targeting of the engineered Beclin 1 constructs, and the proper formation of autophagy-regulatory Beclin 1 complexes. The ULK kinases are required for autophagy initiation upstream of Beclin 1, and autophagosome biogenesis is severely impaired in ULK1/ULK2 double knockout cells. We tested whether Beclin 1 targeting facilitated its ability to rescue autophagosome formation in ULK1/ULK2 double knockout cells. ER-targeted Beclin 1 was most effective in the rescue experiments, while mitochondria-targeted and non-targeted Beclin 1 also showed an ability to rescue, but with lower activity. However, none of the constructs was able to increase autophagic flux in the knockout cells. We also showed that wild type Beclin 1 was enriched on the ER during autophagy induction, and that ULK1/ULK2 facilitated the ER-enrichment of Beclin 1 under basal conditions. The results suggest that one of the functions of ULK kinases may be to enhance Beclin 1 recruitment to the ER to drive autophagosome formation.
Original languageEnglish
Article number475
JournalCells
Volume8
Issue number5
Number of pages24
ISSN2073-4409
DOIs
Publication statusPublished - 17 May 2019
MoE publication typeA1 Journal article-refereed

Fields of Science

  • 1182 Biochemistry, cell and molecular biology
  • autophagy
  • Beclin 1
  • ULK1
  • ULK2
  • endoplasmic reticulum
  • mitochondria
  • MAMMALIAN AUTOPHAGY
  • COMPLEX
  • PROTEIN
  • MACROAUTOPHAGY
  • IDENTIFICATION
  • MECHANISMS
  • PATHWAYS
  • BINDING
  • FIP200
  • FORMS

Cite this

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title = "ER-Targeted Beclin 1 Supports Autophagosome Biogenesis in the Absence of ULK1 and ULK2 Kinases",
abstract = "Autophagy transports cytoplasmic material and organelles to lysosomes for degradation and recycling. Beclin 1 forms a complex with several other autophagy proteins and functions in the initiation phase of autophagy, but the exact role of Beclin 1 subcellular localization in autophagy initiation is still unclear. In order to elucidate the role of Beclin 1 localization in autophagosome biogenesis, we generated constructs that target Beclin 1 to the endoplasmic reticulum (ER) or mitochondria. Our results confirmed the proper organelle-specific targeting of the engineered Beclin 1 constructs, and the proper formation of autophagy-regulatory Beclin 1 complexes. The ULK kinases are required for autophagy initiation upstream of Beclin 1, and autophagosome biogenesis is severely impaired in ULK1/ULK2 double knockout cells. We tested whether Beclin 1 targeting facilitated its ability to rescue autophagosome formation in ULK1/ULK2 double knockout cells. ER-targeted Beclin 1 was most effective in the rescue experiments, while mitochondria-targeted and non-targeted Beclin 1 also showed an ability to rescue, but with lower activity. However, none of the constructs was able to increase autophagic flux in the knockout cells. We also showed that wild type Beclin 1 was enriched on the ER during autophagy induction, and that ULK1/ULK2 facilitated the ER-enrichment of Beclin 1 under basal conditions. The results suggest that one of the functions of ULK kinases may be to enhance Beclin 1 recruitment to the ER to drive autophagosome formation.",
keywords = "1182 Biochemistry, cell and molecular biology, autophagy, Beclin 1, ULK1, ULK2, endoplasmic reticulum, mitochondria, MAMMALIAN AUTOPHAGY, COMPLEX, PROTEIN, MACROAUTOPHAGY, IDENTIFICATION, MECHANISMS, PATHWAYS, BINDING, FIP200, FORMS",
author = "Tahira Anwar and Xiaonan Liu and Taina Suntio and Annika Marjam{\"a}ki and Joanna Biazik and Chan, {Edmond Y. W.} and Markku Varjosalo and Eeva-Liisa Eskelinen",
year = "2019",
month = "5",
day = "17",
doi = "10.3390/cells8050475",
language = "English",
volume = "8",
journal = "Cells",
issn = "2073-4409",
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number = "5",

}

ER-Targeted Beclin 1 Supports Autophagosome Biogenesis in the Absence of ULK1 and ULK2 Kinases. / Anwar, Tahira; Liu, Xiaonan; Suntio, Taina; Marjamäki, Annika; Biazik, Joanna; Chan, Edmond Y. W.; Varjosalo, Markku; Eskelinen, Eeva-Liisa.

In: Cells, Vol. 8, No. 5, 475, 17.05.2019.

Research output: Contribution to journalArticleScientificpeer-review

TY - JOUR

T1 - ER-Targeted Beclin 1 Supports Autophagosome Biogenesis in the Absence of ULK1 and ULK2 Kinases

AU - Anwar, Tahira

AU - Liu, Xiaonan

AU - Suntio, Taina

AU - Marjamäki, Annika

AU - Biazik, Joanna

AU - Chan, Edmond Y. W.

AU - Varjosalo, Markku

AU - Eskelinen, Eeva-Liisa

PY - 2019/5/17

Y1 - 2019/5/17

N2 - Autophagy transports cytoplasmic material and organelles to lysosomes for degradation and recycling. Beclin 1 forms a complex with several other autophagy proteins and functions in the initiation phase of autophagy, but the exact role of Beclin 1 subcellular localization in autophagy initiation is still unclear. In order to elucidate the role of Beclin 1 localization in autophagosome biogenesis, we generated constructs that target Beclin 1 to the endoplasmic reticulum (ER) or mitochondria. Our results confirmed the proper organelle-specific targeting of the engineered Beclin 1 constructs, and the proper formation of autophagy-regulatory Beclin 1 complexes. The ULK kinases are required for autophagy initiation upstream of Beclin 1, and autophagosome biogenesis is severely impaired in ULK1/ULK2 double knockout cells. We tested whether Beclin 1 targeting facilitated its ability to rescue autophagosome formation in ULK1/ULK2 double knockout cells. ER-targeted Beclin 1 was most effective in the rescue experiments, while mitochondria-targeted and non-targeted Beclin 1 also showed an ability to rescue, but with lower activity. However, none of the constructs was able to increase autophagic flux in the knockout cells. We also showed that wild type Beclin 1 was enriched on the ER during autophagy induction, and that ULK1/ULK2 facilitated the ER-enrichment of Beclin 1 under basal conditions. The results suggest that one of the functions of ULK kinases may be to enhance Beclin 1 recruitment to the ER to drive autophagosome formation.

AB - Autophagy transports cytoplasmic material and organelles to lysosomes for degradation and recycling. Beclin 1 forms a complex with several other autophagy proteins and functions in the initiation phase of autophagy, but the exact role of Beclin 1 subcellular localization in autophagy initiation is still unclear. In order to elucidate the role of Beclin 1 localization in autophagosome biogenesis, we generated constructs that target Beclin 1 to the endoplasmic reticulum (ER) or mitochondria. Our results confirmed the proper organelle-specific targeting of the engineered Beclin 1 constructs, and the proper formation of autophagy-regulatory Beclin 1 complexes. The ULK kinases are required for autophagy initiation upstream of Beclin 1, and autophagosome biogenesis is severely impaired in ULK1/ULK2 double knockout cells. We tested whether Beclin 1 targeting facilitated its ability to rescue autophagosome formation in ULK1/ULK2 double knockout cells. ER-targeted Beclin 1 was most effective in the rescue experiments, while mitochondria-targeted and non-targeted Beclin 1 also showed an ability to rescue, but with lower activity. However, none of the constructs was able to increase autophagic flux in the knockout cells. We also showed that wild type Beclin 1 was enriched on the ER during autophagy induction, and that ULK1/ULK2 facilitated the ER-enrichment of Beclin 1 under basal conditions. The results suggest that one of the functions of ULK kinases may be to enhance Beclin 1 recruitment to the ER to drive autophagosome formation.

KW - 1182 Biochemistry, cell and molecular biology

KW - autophagy

KW - Beclin 1

KW - ULK1

KW - ULK2

KW - endoplasmic reticulum

KW - mitochondria

KW - MAMMALIAN AUTOPHAGY

KW - COMPLEX

KW - PROTEIN

KW - MACROAUTOPHAGY

KW - IDENTIFICATION

KW - MECHANISMS

KW - PATHWAYS

KW - BINDING

KW - FIP200

KW - FORMS

U2 - 10.3390/cells8050475

DO - 10.3390/cells8050475

M3 - Article

VL - 8

JO - Cells

JF - Cells

SN - 2073-4409

IS - 5

M1 - 475

ER -