Mitochondria-associated endoplasmic reticulum membranes (MAMs) are the physical connection sites between mitochondria and endoplasmic reticulum (ER). As the compartments controlling substance and information communications between ER and mitochondria, MAMs were involved in the regulation of various pathophysiological processes, such as calcium homeostasis, mitochondrial morphology and function, lipid metabolism and autophagy. In the past decades, accumulating lines of evidence have revealed the pivotal role of MAMs in diverse cardiovascular diseases (CVD). Aging is one of the major independent risk factors for CVD, which causes progressive degeneration of the cardiovascular system, leading to increased morbidity and mortality of CVD. This review aims to summarize the research progress of MAMs in age-related CVD, and explore new targets for its prevention and treatment.
Humans ; Mitochondrial Membranes ; Cardiovascular Diseases/metabolism* ; Calcium Signaling/physiology* ; Mitochondria/physiology* ; Endoplasmic Reticulum/metabolism*

Erythrocytes ; metabolism ; Humans ; Kidney Diseases ; genetics ; metabolism ; Mitochondria ; genetics ; Mitochondrial Membranes ; metabolism ; Oxidative Stress ; genetics ; physiology

The three dimensional structures of both pro-apoptotic Bax and anti-apoptotic Bcl-2 are strikingly similar to that of pore-forming domains of diphtheria toxin and E. coli colicins. Consistent with the structural similarity, both Bax and Bcl-2 have been shown to possess pore-forming property in the membrane. However, these pore-forming proteins form pores via different mechanisms. While Bax and diphtheria toxin form pores via oligomerization, the colicin pore is formed only by colicin monomers. Although the oligomers of Bcl-2 proteins have been found in the mitochondria of both healthy and apoptotic cells, it is unknown whether or not oligomerization is involved in the pore formation. To determine the mechanism of Bcl-2 pore formation, we reconstituted the pore-forming process of Bcl-2 using purified proteins and liposomes. We found that Bcl-2 pore size depended on Bcl-2 concentration, and the release of smaller entrapped molecules was faster than that of larger ones from liposomes at a given Bcl-2 concentration. Moreover, the rate of dye release mediated by pre-formed wild-type Bcl-2 oligomers or by the mutant Bcl-2 monomers with a higher homo-association affinity was much higher than that by wild-type Bcl-2 monomers. Together, it is suggested that oligomerization is likely involved in Bcl-2 pore formation.
Apoptosis ; physiology ; Cytosol ; metabolism ; Humans ; Hydrogen-Ion Concentration ; Liposomes ; metabolism ; Mitochondrial Membrane Transport Proteins ; metabolism ; Mitochondrial Membranes ; metabolism ; Protein Multimerization ; Proto-Oncogene Proteins c-bcl-2 ; metabolism

OBJECTIVETo explore the intervention effect and the possibly mechanism of the glutamine (Gln) on the opening change of the permeability transition pore (PTP) in the myocardial mitochondrial membrane under the overtraining state.

METHODS30 SD rats were randomly divided into 3 groups (n = 10): control group (CG group), overtraining group (OG group) and supplementary (Gln) + overtraining group group). Spectrophotometry was used to test the openness of the permeability transition pore in the myocardial mitochondrial membrane. Electrochemistry was used to test the malondialdehyde (MDA) and the glutathione (GSH) content and the phospholipase A2 (PLA2) activity.

RESULTSOG group compared with the GOG group, the absorbance (A0) and the absorbance change (Delta A) were decreased significantly (P < 0.05). Rh123 fluorescence (F0) intensity was significantly increased (P < 0.05). Rhodamine123 (Rh123) fluorescence change (delta F) was significantly decreased (P < 0.05). Compared with the GOG, the mitochondrial GSH was significantly decreased (P < 0.05), the PLA2 activity and the content of MDA were significantly increased (P <0.05).

CONCLUSIONOvertraining could lead to opening increase of permeability transition pore in the myocardial mitochondrial membrane, after overtraining, the production of the reactive oxygen species (ROS) and PLA2 activity were increased, GSH content was decreased. But added exogenous Gln had a significant intervention effect for these changes.

Animals ; Glutamine ; pharmacology ; Glutathione ; metabolism ; Male ; Mitochondria, Heart ; drug effects ; physiology ; Mitochondrial Membrane Transport Proteins ; metabolism ; Mitochondrial Membranes ; drug effects ; physiology ; Myocardium ; metabolism ; Permeability ; Rats ; Rats, Sprague-Dawley ; Reactive Oxygen Species ; metabolism

Metaxin, a mitochondrial outer membrane protein, is critical for TNF-induced cell death in L929 cells. Its deficiency, caused by retroviral insertion-mediated mutagenesis, renders L929 cells resistance to TNF killing. In this study, we further characterized metaxin deficiency-caused TNF resistance in parallel with Bcl-X(L) overexpression-mediated death resistance. We did not find obvious change in mitochondria membrane potential in metaxin-deficient (Met(mut)) and Bcl-X(L)-overexpressing cells, but we did find an increase in the release rate of the mitochondrial membrane potential probe rhodamine 123 (Rh123) that was preloaded into mitochondria. In addition, overexpression of a function-interfering mutant of metaxin (MetaΔTM/C) or Bcl-X(L) in MCF-7.3.28 cells also resulted in an acquired resistance to TNF killing and a faster rate of Rh123 release, indicating a close correlation between TNF resistance and higher rates of the dye release from the mitochondria. The release of Rh123 can be controlled by the mitochondrial membrane permeability transition (PT) pore, as targeting an inner membrane component of the PT pore by cyclosporin A (CsA) inhibited Rh123 release. However, metaxin deficiency and Bcl-X(L) overexpression apparently affect Rh123 release from a site(s) different from that of CsA, as CsA can overcome their effect. Though both metaxin and Bcl-X(L) appear to function on the outer mitochondrial membrane, they do not interact with each other. They may use different mechanisms to increase the permeability of Rh123, since previous studies have suggested that metaxin may influence certain outer membrane porins while Bcl-X(L) may form pores on the outer membrane. The alteration of the mitochondrial outer membrane properties by metaxin deficiency and Bcl-X(L) overexpression, as indicated by a quicker Rh123 release, may be helpful in maintaining mitochondrial integrity.
Animals ; Apoptosis ; Cell Line, Tumor ; Cell Membrane Permeability ; Humans ; Membrane Potential, Mitochondrial ; physiology ; Mice ; Mitochondrial Membrane Transport Proteins ; physiology ; Mitochondrial Membranes ; metabolism ; Mutation ; Necrosis ; Proteins ; genetics ; metabolism ; Reactive Oxygen Species ; metabolism ; Rhodamine 123 ; metabolism ; Tumor Necrosis Factor-alpha ; pharmacology ; physiology ; bcl-X Protein ; metabolism

Apoptosis/*drug effects/physiology ; BH3 Interacting Domain Death Agonist Protein/physiology ; Drug Design ; Genes, bcl-2 ; Humans ; Mitochondria/physiology/ultrastructure ; Mitochondrial Membranes/*metabolism/physiology ; Multigene Family ; Proto-Oncogene Proteins c-bcl-2/*antagonists & inhibitors ; Signal Transduction

A vast portion of human disease results when the process of apoptosis is defective. Disorders resulting from inappropriate cell death range from autoimmune and neurodegenerative conditions to heart disease. Conversely, prevention of apoptosis is the hallmark of cancer and confounds the efficacy of cancer therapeutics. In the search for optimal targets that would enable the control of apoptosis, members of the BCL-2 family of anti- and pro-apoptotic factors have figured prominently. Development of BCL-2 antisense approaches, small molecules, and BH3 peptidomimetics has met with both success and failure. Success-because BCL-2 proteins play essential roles in apoptosis. Failure-because single targets for drug development have limited scope. By examining the activity of the BCL-2 proteins in relation to the mitochondrial landscape and drawing attention to the significant mitochondrial membrane alterations that ensue during apoptosis, we demonstrate the need for a broader based multi-disciplinary approach for the design of novel apoptosis-modulating compounds in the treatment of human disease.
Apoptosis/*drug effects/physiology ; BH3 Interacting Domain Death Agonist Protein/physiology ; Drug Design ; Genes, bcl-2 ; Humans ; Mitochondria/physiology/ultrastructure ; Mitochondrial Membranes/*metabolism/physiology ; Multigene Family ; Proto-Oncogene Proteins c-bcl-2/*antagonists & inhibitors ; Signal Transduction

Pore-formation and protein-protein interactions are considered to play critical roles in the regulation of apoptosis by Bcl-2 family proteins. During the initiation of apoptosis, the anti-apoptotic Bcl-2 and the pro-apoptotic Bax form different pores to regulate the permeability of mitochondrial outer membrane, playing their opposite functions. Overexpression of Bcl-2 has been found in various cancer cells, therefore it is gaining widespread interest to discover small molecules to compromise Bcl-2 function for anti-cancer treatment. Since Bax binds to Bcl-2's hydrophobic groove via its BH3 domain (composed of helices 2 and 3), by which their functions are inhibited each other, the H2-H3 peptide that contains the functional BH3 domain of Bax has been considered as a potential Bcl-2 antagonist. We recently reported that Bax peptide H2-H3 promotes cell death by inducing Bax-mediated cytochrome c release and by antagonizing Bcl-2's inhibitory effect on Bax. However, the mechanism of how H2-H3 inhibits the anti-apoptotic activity of Bcl-2 remains poorly understood. To address this question, we reconstituted the Bcl-2 or Bax pore-forming process in vitro. We found that H2-H3 inhibited Bcl-2's pore formation and neutralized Bcl-2's inhibitory effect on Bax pore formation in the membrane, whereas the mutant H2-H3 peptide that does not induce apoptosis in cells was shown to have no effect on Bcl-2's activities. Thus, inhibiting Bcl-2's pore-forming and anti-Bax activities in the membrane is strongly correlated with H2-H3's pro-apoptosis function in cells.
Apoptosis ; physiology ; BH3 Interacting Domain Death Agonist Protein ; chemistry ; Humans ; Membrane Proteins ; chemistry ; metabolism ; Mitochondrial Membrane Transport Proteins ; Mitochondrial Membranes ; metabolism ; Proto-Oncogene Proteins c-bcl-2 ; antagonists & inhibitors ; chemistry ; bcl-2 Homologous Antagonist-Killer Protein ; chemistry ; bcl-2-Associated X Protein ; chemistry