Related Experiment Video
Updated: Jun 17, 2026

Subcellular Fractionation for ERK Activation Upon Mitochondrial-derived Peptide Treatment
Published on: September 25, 2017
Phosphorylated hamartin-Hsp70 complex regulates apoptosis via mitochondrial localization.
Hirofumi Inoue1, Takumi Uyama, Tsukasa Suzuki
1Department of Applied Biology and Chemistry, Tokyo University of Agriculture, 1-1-1 Sakuragaoka, Setagaya-ku, Tokyo 156-8502, Japan.
Hamartin, a Tuberous Sclerosis Complex (TSC) protein, inhibits apoptosis by localizing to mitochondria. This process requires hamartin phosphorylation and binding to Heat Shock Protein 70 (Hsp70).
Area of Science:
- Cell Biology
- Molecular Biology
- Genetics
Background:
- Tuberous Sclerosis Complex (TSC) proteins, hamartin and tuberin, form a heterodimer.
- Hamartin's interaction with Heat Shock Protein 70 (Hsp70) was previously reported but its physiological role was unclear.
Purpose of the Study:
- To elucidate the physiological implications of the hamartin-Hsp70 interaction.
- To investigate the role of hamartin localization and phosphorylation in apoptosis regulation.
Main Methods:
- Immunofluorescence to determine hamartin localization.
- Site-directed mutagenesis to create non-phosphorylatable hamartin mutants.
- Apoptosis assays and Hsp70 inhibitor treatment.
Main Results:
- Hamartin localizes to the outer mitochondrial membrane in an Hsp70-dependent manner.
- Phosphorylation of hamartin at residue T417 is crucial for mitochondrial localization and Hsp70 interaction.
- Mutants unable to be phosphorylated at T417 failed to localize to mitochondria and suppress apoptosis.
- Non-phosphorylatable mutants promoted apoptosis upon Hsp70 inhibition.
Conclusions:
- Hamartin inhibits apoptosis through mitochondrial localization.
- Hamartin phosphorylation and Hsp70 binding are essential for its anti-apoptotic function.
More Related Videos
09:18Identification of Intracellular Signaling Events Induced in Viable Cells by Interaction with Neighboring Cells Undergoing Apoptotic Cell Death
Published on: December 27, 2016
19:44Enhancement of Apoptotic and Autophagic Induction by a Novel Synthetic C-1 Analogue of 7-deoxypancratistatin in Human Breast Adenocarcinoma and Neuroblastoma Cells with Tamoxifen
Published on: May 30, 2012
Related Concept Videos
PI3K/mTOR/AKT Signaling Pathway
The JAK-STAT Signaling Pathway
The Intrinsic Apoptotic Pathway
Energy to Drive Translocation
Generally, polypeptides are unfolded by two distinct...
Translocation of Proteins into the Mitochondria
Sorting of outer membrane proteins:
Mitochondrial outer membrane proteins are of two types: the transmembrane, beta-barrel porins, and the membrane-anchored, alpha-helical proteins. Beta-barrel porin precursors are translocated by the TOM complex and inserted into the outer mitochondrial membrane by the SAM complex. In contrast,...
Protein Kinases and Phosphatases
Protein kinases
Many proteins in the cell are regulated by phosphorylation, the addition of a phosphate group. A family of enzymes called kinases...