A complex of Shc and Ran-GTPase localises to the cell nucleus

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• The adaptor protein Shc exists in three isoforms with varied roles in cell signaling.
• The p46 Shc isoform has been observed in the nuclei of hepatocellular carcinoma cells, indicating a non-cytoplasmic function.
• Mechanisms and ligands facilitating Shc isoform nuclear transport remain largely uncharacterized.

Purpose of the Study:

• To identify ligands responsible for the nuclear transport of Shc isoforms.
• To elucidate the molecular interactions governing Shc nuclear localization.

Main Methods:

• Far western blotting was employed to determine the p52 Shc interactome.
• In vitro binding assays assessed the interaction between p52 Shc and identified proteins.
• Co-immunoprecipitation, pull-down assays, and fluorescence lifetime imaging microscopy (FLIM) were used in stable cell lines to confirm interactions and localization.

Main Results:

• The Ran-GTPase nuclear transport protein was identified as a binding partner for p52 Shc, exhibiting low micromolar affinity in vitro.
• Cellular interaction and nuclear localization of Shc were confirmed through co-immunoprecipitation, pull-down, and FLIM experiments.
• The nuclear transport factor NTF2 was found to form a complex with both Ran and Shc.

Conclusions:

• Ran-GTPase directly interacts with p52 Shc.
• The formation of a tertiary complex involving Ran, NTF2, and Shc suggests a novel pathway for Shc nuclear import.
• This finding provides insight into the distinct roles of Shc isoforms in cellular processes, particularly in the context of cancer cells.