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Functional diversity of FGF-2 isoforms by intracellular sorting.
Vigdis Sørensen1, Trine Nilsen, Antoni Wiedłocha
1Department of Biochemistry, Institute for Cancer Research, The Norwegian Radium Hospital, University of Oslo, Norway.
Summary
Fibroblast growth factor 2 (FGF-2) exhibits distinct intracellular and extracellular functions based on its isoform. High molecular weight FGF-2 acts intracrine in the nucleus, while the 18 kDa form functions as a growth factor and can signal via endocytosis.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Protein localization regulates biological activity.
- Fibroblast growth factor 2 (FGF-2) exists in multiple isoforms due to alternative translation initiation.
- Isoforms of FGF-2 are differentially sorted within cells, impacting their functions.
Purpose of the Study:
- To discuss the mode of action of intracellular FGF-2.
- To elucidate the biological role of intracellular FGF-2.
- To differentiate the functions of high molecular weight and 18 kDa FGF-2 isoforms.
Main Methods:
- Analysis of protein translation and initiation.
- Cellular localization studies.
- Investigation of protein-receptor interactions and endocytosis pathways.
Main Results:
- High molecular weight FGF-2 isoforms are retained intracellularly and translocate to the nucleus for intracrine signaling.
- The 18 kDa FGF-2 isoform is secreted and acts as a conventional growth factor via cell-surface receptors.
- Exogenous FGF-2, internalized through receptor-mediated endocytosis, can reach the nucleus and transmit mitogenic signals.
Conclusions:
- FGF-2's subcellular localization dictates its biological activity, acting either intracrine or as an extracellular growth factor.
- Intracellular FGF-2 interacts with various cellular proteins, influencing cell growth and behavior.
- Understanding FGF-2 trafficking is crucial for comprehending its diverse roles in cell signaling.