Omori 2016 Abstract Mito Xmas Meeting Innsbruck: Difference between revisions

Latest revision as of 11:11, 7 December 2016

Exploring the role of mitochondrial dynamics in melanocytes and melanomas.

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Omori A, Migliorini D, Scorrano L (2016)

Event: Mito Xmas Meeting 2016 Innsbruck AT

Melanin, the pigment that colors the skin, hair and eyes, is made by cells called melanocytes. Melanin serves multiple purposes, one of which is skin protection against UV irradiation [1]. However, melanocytes can become origins of melanoma, the most aggressive type of skin cancer with high mortality. Despite recent advances in cancer research, there are only few effective treatments for melanoma. It has been shown that aging symptoms, such as hair graying, are caused by defective self-maintenance of melanocyte stem cells (MSC). In fact, Bcl2 deficiency causes selective apoptosis in the MSC and accelerates hair graying. The anti-apoptotic Bcl2 protein suppresses cytochrome c release from mitochondrial cristae [2,3]. These reports suggest that mitochondria play important roles for melanocyte/MSC survival.

Mitochondrial fission and fusion (mitochondrial dynamics) play critical roles in maintaining functional mitochondria. Mitochondrial dynamics are regulated by ubiquitously expressed Dynamin-related GTPases. Dynamin related protein1 mediates fission, while Mitofusin 1 and 2 in the outer mitochondrial membrane and Optic atrophy (Opa1) mediate fusion. However, the involvement of mitochondrial dynamics on melanocyte regulation and growth of melanoma is poorly known.

Despite the well-known role of Bcl2, the anti apoptotic role of Opa1, which keeps cristae structures tight and suppresses cytochrome c release, is less well established in melanocytes and melanoma. Remarkably, we found a significant increase of Opa1 in several cancer melanoma cell lines. We also observed the gray hair syndrome in melanocyte specific Opa1 mutants. These data suggest important functions of Opa1 in melanocytes and highlights a new potential therapeutic target for melanoma.

Labels: MiParea: mt-Structure;fission;fusion Pathology: Cancer

Event: A1, Oral

Affiliations

Omori A(1,2), Migliorini D(1), Scorrano L(1,2)

Dept Biochem, Univ Padova, Italy
VIMM, Venetian Inst Mol Med, Padova, Italy

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 {{Abstract
-|title=Methods for evaluation of mitochondrial membrane potential with multi-sensor high-resolution respirometry: potentiometry vs fluorometry.
+|title=Exploring the role of mitochondrial dynamics in melanocytes and melanomas.
-|authors=Sumbalova Z , Krumschnabel G, Gnaiger E
+|authors=Omori A, Migliorini D, Scorrano L
 |year=2016
 |event=Mito Xmas Meeting 2016 Innsbruck AT
-|abstract=Under physiological conditions mitochondrial (mt) membrane potential (Δ''Ψ''<sub>mt</sub>) is maintained within a healthy range compatible with major mt functions [1]. In pathophysiological states, elevated values of Δ''Ψ''<sub>mt</sub> may be associated with increased production of reactive oxygen species, while diminished Δ''Ψ''<sub>mt</sub> values compromise mt ATP generation and Ca2+ retention capacity. Absolute values of Δ''Ψ''<sub>mt</sub> depend on available substrates and the prevailing coupling state of a mt preparation [2]. Details of the interrelationship between respiratory states and Δ''Ψ''<sub>mt</sub> can be studied using high-resolution respirometry (HRR) combined with potentiometric or fluorometric detection of Δ''Ψ''<sub>mt</sub>.
+|abstract=Melanin, the pigment that colors the skin, hair and eyes, is made by cells called melanocytes. Melanin serves multiple purposes, one of which is skin protection against UV irradiation [1]. However, melanocytes can become origins of melanoma, the most aggressive type of skin cancer with high mortality. Despite recent advances in cancer research, there are only few effective treatments for melanoma. It has been shown that aging symptoms, such as hair graying, are caused by defective self-maintenance of melanocyte stem cells (MSC). In fact, Bcl2 deficiency causes selective apoptosis in the MSC and accelerates hair graying. The anti-apoptotic Bcl2 protein suppresses cytochrome c release from mitochondrial cristae [2,3]. These reports suggest that mitochondria play important roles for melanocyte/MSC survival.
-Methods for measurement of Δ''Ψ''<sub>mt</sub> depend on the addition of a reporter ion. For the potentiometric approach, the tetraphenylphosphonium ion (TPP<sup>+</sup>) is frequently used, which can be readily detected using an ion sensitive electrode system (OROBOROS ISE-Module). For fluorometric detection of Δ''Ψ''<sub>mt</sub>, fluorescent dyes Safranin [3] or TMRM [4] can be applied with detection of their fluorescence by the OROBOROS O2k-Fluo LED2-Module. Unfortunately, at commonly applied concentrations of 1.5 - 2 µM all these probes interfere with mt respiration to some extent. Inhibition by TPP<sup>+</sup> was found to be the lowest (< 3%) among these three dyes in mouse brain mitochondria. TPP<sup>+</sup> could be successfully used for the simultaneous measurement of respiration and Δ''Ψ''<sub>mt</sub> with NADH-linked substrates (N) and N combined with succinate (NS) [5], whereas limited sensitivity of potentiometric method at low Δ''Ψ''<sub>mt</sub> rendered it unsuitable in combination with succinate (S). In comparison, fluorometric methods using TMRM or Safranin appeared more sensitive in the range of low Δ''Ψ''<sub>mt</sub>, but at the cost of considerable inhibition of mt respiration particularly when employed with N-linked substrates (~30%).
+Mitochondrial fission and fusion (mitochondrial dynamics) play critical roles in maintaining functional mitochondria. Mitochondrial dynamics are regulated by ubiquitously expressed Dynamin-related GTPases. Dynamin related protein1 mediates fission, while Mitofusin 1 and 2 in the outer mitochondrial membrane and Optic atrophy (Opa1) mediate fusion. However, the involvement of mitochondrial dynamics on melanocyte regulation and growth of melanoma is poorly known.
-From the potentiometric TPP<sup>+</sup> experiments absolute values of Δ''Ψ''<sub>mt</sub> [mV] can be calculated, since the signal of the TPP<sup>+</sup> electrode corresponds to the concentration of free TPP<sup>+</sup> outside the mitochondria. In contrast, the fluorescence signal obtained with Safranin or TMRM consists of a mixture of the signal from free and bound probe and thus cannot be considered as a defined dye concentration convertible to mV. For future applications a method can be established for transformation of the fluorescence signal to Δ''Ψ''<sub>mt</sub> for each type of mitochondria and protein concentration, which has to be kept constant in any set of experiments.
+Despite the well-known role of Bcl2, the anti apoptotic role of Opa1, which keeps cristae structures tight and suppresses cytochrome c release, is less well established in melanocytes and melanoma. Remarkably, we found a significant increase of Opa1 in several cancer melanoma cell lines. We also observed the gray hair syndrome in melanocyte specific Opa1 mutants. These data suggest important functions of Opa1 in melanocytes and highlights a new potential therapeutic target for melanoma.
-Both fluorometric and potentiometric measurements can be a valuable tool to distinguish differences in Δ''Ψ''<sub>mt</sub> between experimental groups. Optimization of the experimental approach is possible by selecting the fluorometric or potentiometric approach and corresponding dye according to the specific questions to be addressed and the tissue- and species-specific mitochondrial properties.
-|mipnetlab=AT Innsbruck OROBOROS,
 }}
 {{Labeling
-|area=Respiration
+|area=mt-Structure;fission;fusion
-|topics=mt-Membrane potential
+|diseases=Cancer
-|instruments=Oxygraph-2k, O2k-Fluorometer, TPP
+|event=A1, Oral
-|event=A2, Oral
 }}
 == Affiliations ==
-:::: Sumbalova Z(1,2), Krumschnabel G(1), Gnaiger E(1,3)
+:::: Omori A(1,2), Migliorini D(1), Scorrano L(1,2)
-::::# OROBOROS INSTRUMENTS, Innsbruck, Austria
-::::# Pharmacobiochemical Laboratory, Faculty of Medicine, Comenius University Bratislava, Slovakia
-::::# Department of Visceral, Transplant and  Thoracic Surgery, Daniel Swarovski Research Laboratory, Medical University Innsbruck, Austria
-== References ==
-::::# Nicholls DG (2006) Simultaneous monitoring of ionophore- and inhibitor-mediated plasma and mitochondrial membrane potential changes in cultured neurons. J Biol Chem 281:14864-74.
-::::# Sumbalova Z, Fasching M, Gnaiger E (2011) Substrate control in mitochondrial respiration and regulation of mitochondrial membrane potential. Abstract Mitochondrial Medicine Chicago. (http://wiki.oroboros.at/index.php/Sumbalova_2011_Abstract_Mitochondrial_Medicine)
-::::# Krumschnabel G, Eigentler A, Fasching M, Gnaiger E (2014) Use of safranin for the assessment of mitochondrial membrane potential by high-resolution respirometry and fluorometry. Methods Enzymol 542:163-81.
-::::# Scaduto RC Jr, Grotyohann LW (1999) Measurement of mitochondrial membrane potential using fluorescent rhodamine derivatives. Biophys J 76:469-77.
-::::# Sumbalova Z, Fasching M, Gnaiger E (2012) Evaluation of mitochondrial respiration and membrane potential in mouse brain homogenate. Mitochondr Physiol Network 17.12:61(http://wiki.oroboros.at/index.php/Sumbalova_2012_Abstract_Bioblast)
-== Support ==
+::::# Dept Biochem, Univ Padova, Italy
-:::: Action Austria-Slovakia (SZ) and K-Regio project [[MitoFit]] (GE).
+::::# VIMM, Venetian Inst Mol Med, Padova, Italy