Effects of Cardiolipin on the Conformational Dynamics of Membrane-Anchored Bcl-xL

Abstract

The anti-apoptotic protein Bcl-xL regulates apoptosis by preventing the permeation of the mitochondrial outer membrane by pro-apoptotic pore-forming proteins, which release apoptotic factors into the cytosol that ultimately lead to cell death. Two different membrane-integrated Bcl-xL constructs have been identified: a membrane-anchored and a membrane-inserted conformation. Here, we use molecular dynamics simulations to study the effect of the mitochondrial specific lipid cardiolipin and the protein protonation state on the conformational dynamics of membrane-anchored Bcl-xL. The analysis reveals that the protonation state of the protein and cardiolipin content of the membrane modulate the orientation of the soluble head region (helices α1 through α7) and hence the exposure of its BH3-binding groove, which is required for its interaction with pro-apoptotic proteins.

Balancing life and death: BCL‐2 family members at diverse ER–mitochondrial contact sites

“…CL has also been shown to promote membrane targeting of BCL-X L , as well as MCL-1 and BAK, when using small unilamellar vesicles, supraphysiological concentrations of CL or when combined with BID [249,250]. Once recruited, molecular dynamic simulations suggest that CL might also regulate the function of BCL-X L through exposure of its BH3-binding pocket [251]. It has been proposed that these events occur at OMM-IMM contact points given the relative abundance of CL.…”

Fluorescent Probes and Quenchers in Studies of Protein Folding and Protein‐Lipid Interactions

“…In addition, we foresee an increasing use of the fluorescence spectroscopy in conjunction with various computer simulations, at reconstructing atomistic or near-atomistic processes of physiological and biomedical importance. The first examples of such joined refinements of fluorescence experiments and results of the all-atom MD simulations have been particularly useful for studies of membrane-interacting proteins, [42,46,119,235,[241][242][243] which are notoriously difficult to study by regular structural methods. [223,[234][235] for more detail.…”

Advances in Bcl-xL Research 2.0

“…The targeting of anti-apoptotic Bcl-2 proteins in preclinical studies is reviewed here in the context of melanoma [2] and hematological malignancies [3] Finally, Tyagi et al present a research article in which molecular dynamics simulations are used to study the conformation of Bcl-xL anchored into the membrane, which exhibits a significant degree of structural remodeling of the globular head. The conformational dynamics of Bcl-xL are explored using a protein with all aspartic and glutamic acid and histidine sidechains protonated or deprotonated as this modifies the interaction of Bcl-xL with membranes; the effect of the mitochondrial lipid cardiolipin is also analyzed due to the postulation that it generates hotspots for apoptotic regulation [9]. This work illustrates how considering molecular dynamics is useful for obtaining structural insights into the factors acting on conformational modifications; here, both the protonation of membrane-anchored Bcl-xL and cardiolipin are proposed to be required for the exposure of the BH3-binding groove.…”