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IGF-IR internalizes with Caveolin-1 and PTRF/Cavin in HaCat cells
Barbara Salani1, Mario Passalacqua, Sara Maffioli
1Department of Endocrinology and Medicine (DiSEM), University of Genova, Genova, Italy.
Caveolae proteins Caveolin-1 and PTRF/Cavin are crucial for insulin-like growth factor-I receptor (IGF-IR) internalization. Modulating these proteins may offer new ways to control IGF-IR signaling pathways.
Area of Science:
- Cell biology
- Molecular signaling
- Membrane trafficking
Background:
- Insulin-like growth factor-I receptor (IGF-IR) is a tyrosine kinase receptor involved in cellular processes.
- IGF-IR signaling is regulated by its internalization, a process influenced by caveolae, specialized membrane domains.
- Caveolin-1 (Cav-1) and Polymerase I and Transcript Release Factor I (PTRF/Cavin) are key proteins in caveolae function, but their role in IGF-IR internalization is unclear.
Purpose of the Study:
- To investigate the interaction between IGF-IR, Cav-1, and PTRF/Cavin during receptor internalization.
- To elucidate the specific roles of Cav-1 and PTRF/Cavin in regulating IGF-IR trafficking and cell surface levels.
Main Methods:
- Investigated IGF-IR interaction with Cav-1 and PTRF/Cavin in human Hacat cells using co-immunoprecipitation.
- Utilized siRNA to silence Cav-1 and PTRF/Cavin expression.
- Transfected cells with a mutant Cav-1 (Cav-1Y14F) to assess the role of Cav-1 phosphorylation.
- Examined the effect of Clathrin silencing on IGF-IR internalization.
Main Results:
- IGF-IR internalization induced translocation of Cav-1 and PTRF/Cavin to the cytosol, increasing their interaction with the receptor.
- Silencing Cav-1 or PTRF/Cavin affected IGF-IR internalization rates, with PTRF/Cavin silencing also reducing receptor recovery at the plasma membrane.
- A Cav-1 mutant lacking Tyr14 phosphorylation showed reduced IGF-IR internalization, suggesting a role for Cav-1 phosphorylation.
- Clathrin silencing did not impair IGF-IR internalization, distinguishing the process from clathrin-dependent endocytosis.
Conclusions:
- Caveolae play a significant role in the intracellular trafficking of IGF-IR.
- Cav-1 and PTRF/Cavin are critical regulators of IGF-IR internalization and could serve as distinct therapeutic targets for modulating IGF-IR activity.
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