Genetic screen in Drosophila muscle identifies autophagy-mediated T-tubule remodeling and a Rab2 role in autophagy

Elife. 2017 Jan 7;6:e23367. doi: 10.7554/eLife.23367.

Abstract

Transverse (T)-tubules make-up a specialized network of tubulated muscle cell membranes involved in excitation-contraction coupling for power of contraction. Little is known about how T-tubules maintain highly organized structures and contacts throughout the contractile system despite the ongoing muscle remodeling that occurs with muscle atrophy, damage and aging. We uncovered an essential role for autophagy in T-tubule remodeling with genetic screens of a developmentally regulated remodeling program in Drosophila abdominal muscles. Here, we show that autophagy is both upregulated with and required for progression through T-tubule disassembly stages. Along with known mediators of autophagosome-lysosome fusion, our screens uncovered an unexpected shared role for Rab2 with a broadly conserved function in autophagic clearance. Rab2 localizes to autophagosomes and binds to HOPS complex members, suggesting a direct role in autophagosome tethering/fusion. Together, the high membrane flux with muscle remodeling permits unprecedented analysis both of T-tubule dynamics and fundamental trafficking mechanisms.

Keywords: Drosophila metamorphosis; Rab GTPase; T-tubule; autophagosome-lysosome fusion; autophagy; cell biology; developmental biology; muscle fiber; stem cells.

MeSH terms

  • Animals
  • Autophagy / genetics*
  • Drosophila Proteins / genetics
  • Drosophila Proteins / metabolism
  • Drosophila melanogaster / genetics*
  • Drosophila melanogaster / growth & development
  • Drosophila melanogaster / metabolism
  • Gene Expression Profiling
  • Gene Expression Regulation, Developmental*
  • Lysosomes / metabolism
  • Membrane Fusion
  • Morphogenesis / genetics*
  • Muscles / metabolism*
  • Phagosomes / metabolism
  • Protein Isoforms / genetics
  • Protein Isoforms / metabolism
  • Protein Transport
  • Qa-SNARE Proteins / genetics
  • Qa-SNARE Proteins / metabolism
  • R-SNARE Proteins / genetics
  • R-SNARE Proteins / metabolism
  • RNA, Small Interfering / genetics
  • RNA, Small Interfering / metabolism
  • SNARE Proteins / genetics
  • SNARE Proteins / metabolism
  • Signal Transduction
  • rab GTP-Binding Proteins / genetics
  • rab GTP-Binding Proteins / metabolism
  • rab2 GTP-Binding Protein / antagonists & inhibitors
  • rab2 GTP-Binding Protein / genetics
  • rab2 GTP-Binding Protein / metabolism*

Substances

  • Atg8a protein, Drosophila
  • Drosophila Proteins
  • Protein Isoforms
  • Qa-SNARE Proteins
  • R-SNARE Proteins
  • RNA, Small Interfering
  • SNARE Proteins
  • Snap29 protein, Drosophila
  • VAMP7 protein, Drosophila
  • rab7 protein
  • rab GTP-Binding Proteins
  • rab2 GTP-Binding Protein

Grant support

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.