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Hsc70 and Hsp70 interact with phosphatidylserine on the surface of PC12 cells resulting in a decrease of viability.
Nelson Arispe1, Michael Doh, Olga Simakova
1Department of Anatomy, Physiology and Genetics, School of Medicine, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Rd., Bethesda, MD 20814, USA. narispe@usuhs.mil
Summary
Heat shock proteins (HSPs) like Hsp70 interact with cell membranes, potentially accelerating apoptosis. This interaction, particularly with phosphatidylserine, affects cell viability and is influenced by ATP/ADP.
Area of Science:
- Cellular Biology
- Biochemistry
- Membrane Biophysics
Background:
- Heat shock proteins (HSPs) are crucial for protein folding under stress.
- Hsp70 family members exhibit novel lipid-binding properties and membrane channel formation.
- The role of Hsp70 in biological membranes remains largely unexplored.
Purpose of the Study:
- To investigate the interaction of Hsp70 and Hsc70 with cell membranes.
- To determine the functional consequences of Hsp70/Hsc70 membrane incorporation.
- To elucidate the role of Hsp70 in cellular viability and apoptosis.
Main Methods:
- Investigated Hsp70/Hsc70 interaction with lipid bilayers containing phosphatidylserine (PS).
- Assessed the effect of extracellular Hsp70/Hsc70 on cell viability (PC12 cells).
- Examined the influence of ATP/ADP and annexin 5 on Hsp70/Hsc70-induced toxicity.
Main Results:
- Hsp70 and Hsc70 selectively bind and incorporate into membranes rich in phosphatidylserine.
- Extracellular Hsp70/Hsc70 reduces the viability of PS-exposing cells.
- This toxicity is modulated by ATP/ADP and can be blocked by annexin 5.
- PS exposure on cell surfaces correlates with Hsp70/Hsc70-mediated toxicity.
Conclusions:
- Hsp70/Hsc70 interaction with PS-containing membranes may accelerate apoptosis.
- Extracellular Hsp70 may act as an apoptosis accelerator when PS is exposed.
- Findings explain toxicity in Hsp70-overexpressing cells and support regulated Hsp70 expression.