Cargo-mediated regulation of a rapid Rab4-dependent recycling pathway

Mol Biol Cell. 2009 Jun;20(11):2774-84. doi: 10.1091/mbc.e08-08-0892. Epub 2009 Apr 15.

Abstract

Membrane trafficking is well known to regulate receptor-mediated signaling processes, but less is known about whether signaling receptors conversely regulate the membrane trafficking machinery. We investigated this question by focusing on the beta-2 adrenergic receptor (B2AR), a G protein-coupled receptor whose cellular signaling activity is controlled by ligand-induced endocytosis followed by recycling. We used total internal reflection fluorescence microscopy (TIR-FM) and tagging with a pH-sensitive GFP variant to image discrete membrane trafficking events mediating B2AR endo- and exocytosis. Within several minutes after initiating rapid endocytosis of B2ARs by the adrenergic agonist isoproterenol, we observed bright "puffs" of locally increased surface fluorescence intensity representing discrete Rab4-dependent recycling events. These events reached a constant frequency in the continuous presence of isoproterenol, and agonist removal produced a rapid (observed within 1 min) and pronounced (approximately twofold) increase in recycling event frequency. This regulation required receptor signaling via the cAMP-dependent protein kinase (PKA) and a specific PKA consensus site located in the carboxyl-terminal cytoplasmic tail of the B2AR itself. B2AR-mediated regulation was not restricted to this membrane cargo, however, as transferrin receptors packaged in the same population of recycling vesicles were similarly affected. In contrast, net recycling measured over a longer time interval (10 to 30 min) was not detectably regulated by B2AR signaling. These results identify rapid regulation of a specific recycling pathway by a signaling receptor cargo.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Adrenergic beta-2 Receptor Antagonists
  • Adrenergic beta-Agonists / pharmacology
  • Animals
  • Cell Line
  • Cells, Cultured
  • Cyclic AMP-Dependent Protein Kinases / genetics
  • Cyclic AMP-Dependent Protein Kinases / metabolism
  • Endocytosis / physiology*
  • Exocytosis / physiology*
  • Green Fluorescent Proteins / genetics
  • Green Fluorescent Proteins / metabolism
  • Humans
  • Hydrogen-Ion Concentration
  • Isoproterenol / pharmacology
  • Microscopy, Fluorescence / methods
  • Mutation
  • Neurons / cytology
  • Neurons / metabolism
  • Protein Transport / drug effects
  • Rats
  • Receptors, Adrenergic, beta-2 / genetics
  • Receptors, Adrenergic, beta-2 / metabolism
  • Receptors, Transferrin / genetics
  • Receptors, Transferrin / metabolism
  • Signal Transduction / drug effects
  • Signal Transduction / physiology*
  • Time Factors
  • rab4 GTP-Binding Proteins / metabolism*

Substances

  • Adrenergic beta-2 Receptor Antagonists
  • Adrenergic beta-Agonists
  • Receptors, Adrenergic, beta-2
  • Receptors, Transferrin
  • Green Fluorescent Proteins
  • Cyclic AMP-Dependent Protein Kinases
  • rab4 GTP-Binding Proteins
  • Isoproterenol