The anti-apoptotic protein HAX-1 interacts with SERCA2 and regulates its protein levels to promote cell survival.

Abstract

Cardiac contractility is regulated through the activity of various key Ca(2+)-handling proteins. The sarco(endo)plasmic reticulum (SR) Ca(2+) transport ATPase (SERCA2a) and its inhibitor phospholamban (PLN) control the uptake of Ca(2+) by SR membranes during relaxation. Recently, the antiapoptotic HS-1-associated protein X-1 (HAX-1) was identified as a binding partner of PLN, and this interaction was postulated to regulate cell apoptosis. In the current study, we determined that HAX-1 can also bind to SERCA2. Deletion mapping analysis demonstrated that amino acid residues 575-594 of SERCA2's nucleotide binding domain are required for its interaction with the C-terminal domain of HAX-1, containing amino acids 203-245. In transiently cotransfected human embryonic kidney 293 cells, recombinant SERCA2 was specifically targeted to the ER, whereas HAX-1 selectively concentrated at mitochondria. On triple transfections with PLN, however, HAX-1 massively translocated to the ER membranes, where it codistributed with PLN and SERCA2. Overexpression of SERCA2 abrogated the protective effects of HAX-1 on cell survival, after hypoxia/reoxygenation or thapsigargin treatment. Importantly, HAX-1 overexpression was associated with down-regulation of SERCA2 expression levels, resulting in significant reduction of apparent ER Ca(2+) levels. These findings suggest that HAX-1 may promote cell survival through modulation of SERCA2 protein levels and thus ER Ca(2+) stores.

• Authors: Elizabeth Vafiadaki, Demetrios A Arvanitis, Stamatis N Pagakis, Vasiliki Papalouka, Despina Sanoudou, Aikaterini Kontrogianni-Konstantopoulos, Evangelia G Kranias
• Journal: Molecular biology of the cell (Mol Biol Cell) Vol. 20 Issue 1 Pg. 306-18 (Jan 2009) ISSN: 1939-4586 [Electronic] United States
• PMID: 18971376 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)

Chemical References

• Adaptor Proteins, Signal Transducing
• Calcium-Binding Proteins
• Enzyme Inhibitors
• HAX1 protein, human
• Oxidants
• Proteins
• phospholamban
• Thapsigargin
• Hydrogen Peroxide
• Sarcoplasmic Reticulum Calcium-Transporting ATPases
• ATP2A2 protein, human
• Calcium

Topics

• Adaptor Proteins, Signal Transducing
• Animals
• Calcium (metabolism)
• Calcium-Binding Proteins (genetics, metabolism)
• Cell Line
• Cell Survival
• Endoplasmic Reticulum (metabolism)
• Enzyme Inhibitors (metabolism)
• Humans
• Hydrogen Peroxide (metabolism)
• Mice
• Mice, Knockout
• Oxidants (metabolism)
• Protein Binding
• Protein Interaction Mapping
• Proteins (genetics, metabolism)
• Sarcoplasmic Reticulum Calcium-Transporting ATPases (genetics, metabolism)
• Thapsigargin (metabolism)