VPS38/UVRAG and ATG14, the variant regulatory subunits of the ATG6/Beclin1-PI3K complexes, are crucial for the biogenesis of the yolk organelles and are transcriptionally regulated in the oocytes of the vector Rhodnius prolixus

PLoS Negl Trop Dis. 2021 Sep 7;15(9):e0009760. doi: 10.1371/journal.pntd.0009760. eCollection 2021 Sep.

Abstract

In insects the reserve proteins are stored in the oocytes into endocytic-originated vesicles named yolk organelles. VPS38/UVRAG and ATG14 are the variant regulatory subunits of two class-III ATG6/Beclin1 PI3K complexes that regulate the recruitment of the endocytic (complex II) and autophagic (complex I) machineries. In a previous work from our group, we found that the silencing of ATG6/Beclin1 resulted in the formation of yolk-deficient oocytes due to defects in the endocytosis of the yolk proteins. Because ATG6/Beclin1 is present in the two above-described PI3K complexes, we could not identify the contributions of each complex to the yolk defective phenotypes. To address this, here we investigated the role of the variant subunits VPS38/UVRAG (complex II, endocytosis) and ATG14 (complex I, autophagy) in the biogenesis of the yolk organelles in the insect vector of Chagas Disease Rhodnius prolixus. Interestingly, the silencing of both genes phenocopied the silencing of ATG6/Beclin1, generating 1) accumulation of yolk proteins in the hemolymph; 2) white, smaller, and yolk-deficient oocytes; 3) abnormal yolk organelles in the oocyte cortex; and 4) unviable F1 embryos. However, we found that the similar phenotypes were the result of a specific cross-silencing effect among the PI3K subunits where the silencing of VPS38/UVRAG and ATG6/Beclin1 resulted in the specific silencing of each other, whereas the silencing of ATG14 triggered the silencing of all three PI3K components. Because the silencing of VPS38/UVRAG and ATG6/Beclin1 reproduced the yolk-deficiency phenotypes without the cross silencing of ATG14, we concluded that the VPS38/UVRAG PI3K complex II was the major contributor to the previously observed phenotypes in silenced insects. Altogether, we found that class-III ATG6/Beclin1 PI3K complex II (VPS38/UVRAG) is essential for the yolk endocytosis and that the subunits of both complexes are under an unknown transcriptional regulatory system.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Beclin-1 / genetics
  • Beclin-1 / metabolism*
  • Chagas Disease / transmission
  • Egg Yolk / physiology
  • Gene Expression Regulation
  • Gene Silencing
  • Insect Proteins / genetics
  • Insect Proteins / metabolism*
  • Insect Vectors / physiology
  • Oocytes / cytology
  • Oocytes / physiology*
  • Organelles / physiology*
  • Phosphatidylinositol 3-Kinases / genetics
  • Phosphatidylinositol 3-Kinases / metabolism*
  • Rhodnius / physiology*

Substances

  • Beclin-1
  • Insect Proteins

Grants and funding

This work was funded by the following grants. Fundação Carlos Chagas Filho De Amparo À Pesquisa Do Estado Do Rio De Janeiro (FAPERJ) (JCNE E-26/2031802017; http://www.faperj.br/) to I.R.; Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) (INCT-EM 16/2014; http://cnpq.br/) to I.R.; Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) (https://www.gov.br/capes/pt-br) to I.R. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.