Pro-apoptotic cBid and Bax exhibit distinct membrane remodeling activities: An AFM study

Joseph D Unsay; Katia Cosentino; Katharina Sporbeck; Ana J García-Sáez

doi:10.1016/j.bbamem.2016.10.007

Pro-apoptotic cBid and Bax exhibit distinct membrane remodeling activities: An AFM study

Biochim Biophys Acta Biomembr. 2017 Jan;1859(1):17-27. doi: 10.1016/j.bbamem.2016.10.007. Epub 2016 Oct 15.

Authors

Joseph D Unsay¹, Katia Cosentino², Katharina Sporbeck³, Ana J García-Sáez⁴

Affiliations

¹ Interfaculty Institute of Biochemistry, University of Tübingen, Hoppe-Seyler-Str. 4, 72076 Tübingen, Germany; Max Planck Institute for Intelligent Systems, Heisenbergstr. 3, 70569 Stuttgart, Germany; German Cancer Research Center, Im Neuenheimer Feld 280, 69120 Heidelberg, Germany.
² Interfaculty Institute of Biochemistry, University of Tübingen, Hoppe-Seyler-Str. 4, 72076 Tübingen, Germany; Max Planck Institute for Intelligent Systems, Heisenbergstr. 3, 70569 Stuttgart, Germany.
³ Interfaculty Institute of Biochemistry, University of Tübingen, Hoppe-Seyler-Str. 4, 72076 Tübingen, Germany.
⁴ Interfaculty Institute of Biochemistry, University of Tübingen, Hoppe-Seyler-Str. 4, 72076 Tübingen, Germany; Max Planck Institute for Intelligent Systems, Heisenbergstr. 3, 70569 Stuttgart, Germany. Electronic address: ana.garcia@uni-tuebingen.de.

PMID: 27755971
DOI: 10.1016/j.bbamem.2016.10.007

Abstract

Bcl-2 proteins are key regulators of the mitochondrial outer membrane (MOM) permeabilization that mediates apoptosis. During apoptosis, Bid is cleaved (cBid) and translocates to the MOM, where it activates Bax. Bax then oligomerizes and induces MOM permeabilization. However, little is known about how these proteins affect membrane organization aside from pore formation. In previous studies, we have shown that both cBid and Bax are able to remodel membranes and stabilize curvature. Here, we dissected the independent effects of Bax and cBid on supported lipid structures mimicking the mitochondrial composition by means of atomic force spectroscopy. We show that cBid did not permeabilize the membrane but lowered the membrane breakthrough force. On the other hand, Bax effects were dependent on its oligomeric state. Monomeric Bax did not affect the membrane properties. In contrast, oligomeric Bax lowered the breakthrough force of the membrane, which in the context of pore formation, implies a lowering of the line tension at the edge of the pore.

Keywords: Atomic force microscopy (AFM); Bcl-2 proteins; Force spectroscopy; Membrane; supported lipid bilayers.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Animals
Apoptosis
BH3 Interacting Domain Death Agonist Protein / chemistry*
BH3 Interacting Domain Death Agonist Protein / genetics
BH3 Interacting Domain Death Agonist Protein / metabolism
Cardiolipins / chemistry
Cardiolipins / metabolism
Escherichia coli / genetics
Escherichia coli / metabolism
Gene Expression
Humans
Liposomes / chemistry*
Liposomes / metabolism
Mice
Microscopy, Atomic Force
Mitochondria / chemistry
Mitochondria / metabolism
Mitochondrial Membranes / chemistry*
Mitochondrial Membranes / metabolism
Models, Biological*
Mutation
Permeability
Phosphatidylcholines / chemistry
Phosphatidylcholines / metabolism
Phosphatidylethanolamines / chemistry
Phosphatidylethanolamines / metabolism
Phosphatidylinositols / chemistry
Phosphatidylinositols / metabolism
Phosphatidylserines / chemistry
Phosphatidylserines / metabolism
Protein Multimerization
Recombinant Proteins / chemistry
Recombinant Proteins / genetics
Recombinant Proteins / metabolism
bcl-2-Associated X Protein / chemistry*
bcl-2-Associated X Protein / genetics
bcl-2-Associated X Protein / metabolism

Substances

BAX protein, human
BH3 Interacting Domain Death Agonist Protein
Bid protein, mouse
Cardiolipins
Liposomes
Phosphatidylcholines
Phosphatidylethanolamines
Phosphatidylinositols
Phosphatidylserines
Recombinant Proteins
bcl-2-Associated X Protein
phosphatidylethanolamine