Abstract
To examine the acquisition of insulin sensitivity after the initial biosynthesis of the insulin-responsive aminopeptidase (IRAP), 3T3-L1 adipocytes were transfected with an enhanced green fluorescent protein-IRAP (EGFP-IRAP) fusion protein. In the absence of insulin, IRAP was rapidly localized (1-3 h) to secretory membranes and retained in these intracellular membrane compartments with little accumulation at the plasma membrane. However, insulin was unable to induce translocation to the plasma membrane until 6-9 h after biosynthesis. This was in marked contrast to another type II membrane protein (syntaxin 3) that rapidly defaulted to the plasma membrane 3 h after expression. In parallel with the time-dependent acquisition of insulin responsiveness, the newly synthesized IRAP protein converted from a brefeldin A-sensitive to a brefeldin A-insensitive state. The initial trafficking of IRAP to the insulin-responsive compartment was independent of plasma membrane endocytosis, as expression of a dominant-interfering dynamin mutant (Dyn/K44A) inhibited transferrin receptor endocytosis but had no effect on the insulin-stimulated translocation of the newly synthesized IRAP protein.
Original language | English (US) |
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Pages (from-to) | E746-E752 |
Journal | American Journal of Physiology - Endocrinology and Metabolism |
Volume | 289 |
Issue number | 5 52-5 |
DOIs | |
State | Published - Nov 2005 |
Externally published | Yes |
Keywords
- Biosynthesis
- Cargo selection
- Insulin
- Insulin-responsive aminopeptidase
- Trafficking
ASJC Scopus subject areas
- General Medicine