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Abstract
The field of mitochondrial ion channels has undergone a rapid development during the
last three decades, due to the molecular identification of some of the channels residing
in the outer and inner membranes. Relevant information about the function of these
channels in physiological and pathological settings was gained thanks to genetic models
for a few, mitochondria‐specific channels. However, many ion channels have multiple
localizations within the cell, hampering a clear‐cut determination of their function
by pharmacological means. The present review summarizes our current knowledge about
the ins and outs of mitochondrial ion channels, with special focus on the channels
that have received much attention in recent years, namely, the voltage‐dependent anion
channels, the permeability transition pore (also called mitochondrial megachannel),
the mitochondrial calcium uniporter and some of the inner membrane‐located potassium
channels. In addition, possible strategies to overcome the difficulties of specifically
targeting mitochondrial channels versus their counterparts active in other membranes
are discussed, as well as the possibilities of modulating channel function by small
peptides that compete for binding with protein interacting partners. Altogether, these
promising tools along with large‐scale chemical screenings set up to identify new,
specific channel modulators will hopefully allow us to pinpoint the actual function
of most mitochondrial ion channels in the near future and to pharmacologically affect
important pathologies in which they are involved, such as neurodegeneration, ischaemic
damage and cancer. This article is part of a themed section on Mitochondrial Pharmacology:
Featured Mechanisms and Approaches for Therapy Translation. To view the other articles
in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.22/issuetoc
Mitochondria are recognized as one of the most important targets for new drug design in cancer, cardiovascular, and neurological diseases. Currently, the most effective way to deliver drugs specifically to mitochondria is by covalent linking a lipophilic cation such as an alkyltriphenylphosphonium moiety to a pharmacophore of interest. Other delocalized lipophilic cations, such as rhodamine, natural and synthetic mitochondria-targeting peptides, and nanoparticle vehicles, have also been used for mitochondrial delivery of small molecules. Depending on the approach used, and the cell and mitochondrial membrane potentials, more than 1000-fold higher mitochondrial concentration can be achieved. Mitochondrial targeting has been developed to study mitochondrial physiology and dysfunction and the interaction between mitochondria and other subcellular organelles and for treatment of a variety of diseases such as neurodegeneration and cancer. In this Review, we discuss efforts to target small-molecule compounds to mitochondria for probing mitochondria function, as diagnostic tools and potential therapeutics. We describe the physicochemical basis for mitochondrial accumulation of lipophilic cations, synthetic chemistry strategies to target compounds to mitochondria, mitochondrial probes, and sensors, and examples of mitochondrial targeting of bioactive compounds. Finally, we review published attempts to apply mitochondria-targeted agents for the treatment of cancer and neurodegenerative diseases.
Mitochondria are essential organelles with numerous functions in cellular metabolism and homeostasis. Most of the >1,000 different mitochondrial proteins are synthesized as precursors in the cytosol and are imported into mitochondria by five transport pathways. The protein import machineries of the mitochondrial membranes and aqueous compartments reveal a remarkable variability of mechanisms for protein recognition, translocation, and sorting. The protein translocases do not operate as separate entities but are connected to each other and to machineries with functions in energetics, membrane organization, and quality control. Here, we discuss the versatility and dynamic organization of the mitochondrial protein import machineries. Elucidating the molecular mechanisms of mitochondrial protein translocation is crucial for understanding the integration of protein translocases into a large network that controls organelle biogenesis, function, and dynamics.
The presence of cell and tissue barriers together with the low biomembrane permeability of various therapeutics often hampers systemic drug distribution; thus, most of the available molecules are of limited therapeutic value. Opportunities to increase medicament concentrations in areas that are difficult to access now exist with the advent of cell-penetrating peptides (CPPs), which can transport into the cell a wide variety of biologically active conjugates (cargoes). Numerous preclinical evaluations with CPP-derived therapeutics have provided promising results in various disease models that, in some cases, prompted clinical trials. The outcome of these investigations has thus opened new perspectives for CPP application in the development of unprecedented human therapies that are well tolerated and directed to intracellular targets.
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