SAA4: An Underdog Within the Serum Amyloid a Superfamily? Ernst Malle, Corina Madreiter-Sokolowski, Christian Windpassinger International Journal of Molecular Sciences, 2026 Non-glycosylated liver-derived acute-phase amyloid A1 and A2 proteins (SAA1 and SAA2, 104 amino acids), generated by two different genes in humans (SAA1/2) and other mammalian species, are considered the prime acute-phase reactants following inflammatory conditions during host defense in cells, tissues, and the circulation. While human SAA3 has been identified as a pseudogene, Saa3 genes in other mammalian species are coding for primarily extrahepatically expressed Saa3 proteins that also may act as suitable inflammatory markers. The discovery of SAA4 (112 amino acids, carrying an octapeptide insert) in humans and mice has paved a new avenue for the exploration of different functions of this so far unknown member of the SAA superfamily. SAA4 has originally been termed a “constitutively” expressed SAA protein, apparently due to its nature not to act as an inflammatory marker. The present overview aimed to cover possible functions—so far identified—for human SAA4 (following its expression in various diseases on mRNA and protein level) and to work out whether SAA4 might be considered—at least in part—an acute-phase protein. Alternatively, we are raising the question whether SAA4 may solely act as a bystander or even underdog within the whole SAA family, where SAA1 and SAA2 proteins (commonly termed acute-phase SAA) hold undoubtedly an eminent status during inflammatory conditions, not only as host defense reactants but also as long-lasting markers for chronic diseases and malignancies in humans.
Electric field stimulation in Caenorhabditis elegans as a novel approach to investigate mitochondrial Ca2+homeostasis during in vivo muscle aging Sonja Gabrijelčič, Doruntina Bresilla, Fabienne Mossegger, Ernst Malle, Vedran Đerek, Martin Hirtl, Corina T. Madreiter-Sokolowski Methods, 2026 • 10 V/10 s electric pulses evoke [Ca 2+ ] mito transients in C. elegans pharynx. • Electric pulses yield more consistent [Ca 2+ ] mito readouts than caffeine. • Basal and stimulated [Ca 2+ ] mito increase with age, revealing overload risk. • Mitoxantrone reduces age-related [Ca 2+ ] mito overload during repeated stimulation. • Corpus shows stronger MCU-sensitive [Ca 2+ ] mito uptake/overload than posterior bulb. Mitochondrial calcium ([Ca 2+ ] mito ) homeostasis is a key regulator of cellular physiology, controlling signal transduction, energy metabolism, and cell survival. To examine how these processes change with age in vivo , we used the pharyngeal muscle of Caenorhabditis elegans (C. elegans) as a tractable model for studying [Ca 2+ ] mito dynamics. We introduced electric field stimulation as a robust trigger for [Ca 2+ ] mito uptake that overcomes limitations of compound stimulation, which relies on pharyngeal pumping and endoplasmic reticulum store filling and is typically confined to single-stimulus protocols. In contrast, electric field stimulation enables physiologically relevant repeated excitation that challenges [Ca 2+ ] mito uptake and recovery. Stimulation with 10 V for 10 s reliably evoked reproducible [Ca 2+ ] mito transients in the pharyngeal muscle of C. elegans and produced higher responder rates than compound stimulation. Basal [Ca 2+ ] mito increased with age, and the first field-evoked transient was significantly larger in aged animals, an effect not detected with pharmacological triggers. Repeated pulses unmasked cumulative [Ca 2+ ] mito loading and incomplete recovery in aged pharynx, indicative of [Ca 2+ ] mito overload, which was attenuated by inhibition of the mitochondrial Ca 2+ uniporter (MCU) with mitoxantrone. Regional analyses identified the corpus as a hotspot for electric field-evoked [Ca 2+ ] mito uptake and overload, while MCU inhibition reduced repeated responses in both corpus and posterior bulb. Electric field stimulation enables precise, repeated in vivo probing of [Ca 2+ ] mito uptake and recovery, revealing overload in the C. elegans pharynx. This approach identified age-enhanced, MCU-dependent, and region-specific [Ca 2+ ] mito loading, providing a pathophysiologically relevant readout of impaired Ca 2+ handling that may contribute to age-related muscle dysfunction.
Deletion of MMP12 improves energy metabolism and brown adipose tissue function in mice prone to cardiometabolic disease Melina Amor, Malena Diaz, Alexander Fuerlinger, Monika Svecla, Valentina Bianco, Laszlo Schooltink, Anja Dobrijević, Birgit Schwarz, Alena Akhmetshina, Nemanja Vujić, Melanie Korbelius, Martin Hirtl, Martin Buerger, Anita Pirchheim, Silvia Rainer, Silvia Schauer, Giangiacomo Beretta, Walter Goessler, Dagmar Kolb, Gerald Hoefler, Hubert Hackl, Corina Madreiter-Sokolowski, Mahmoud Abdellatif, Giuseppe Danilo Norata, Dagmar Kratky Journal of Lipid Research, 2026 Matrix metalloproteinase-12 (MMP12) is a proinflammatory macrophage-secreted protein with immunomodulatory functions that affects neutrophil infiltration, cytokine release, macrophage recruitment, and proliferation. We have previously demonstrated that the genetic deletion of MMP12 in a cardiometabolic mouse model ameliorates obesity-induced low-grade inflammation, white adipose tissue dysfunction, and atherosclerosis. Based on the various beneficial metabolic effects of MMP-12 deletion, we hypothesized that loss of MMP-12 also positively affects whole-body energy metabolism and/or brown adipose tissue (BAT) function in a cardiometabolic mouse model. To investigate the effects of MMP12 deletion on whole-body energy metabolism and/or BAT function, we used low-density lipoprotein receptor (Ldlr)/Mmp12 double knockout (DKO) fed a high-fat, sucrose- and cholesterol-enriched diet. DKO mice housed at 22°C showed increased energy expenditure and decreased BAT size and triglyceride (TG) content. Untargeted proteomic analyses revealed the upregulation of proteins and pathways related to mitochondrial function, glucose metabolism, and fatty acid oxidation in the BAT of DKO mice, whereas the abundance of proteins and pathways associated with inflammation was reduced. In addition, DKO mice exhibited reduced macrophage infiltration in BAT, with the infiltrating macrophages showing lower expression of lipid-associated marker genes. Loss of MMP12 was associated with reduced compactness and sphericity of the mitochondria in the BAT. Following an acute cold exposure, DKO mice had decreased circulating lipid concentrations, especially very low-density lipoprotein-TG and LDL-cholesterol, and increased expression of thermogenic genes. We conclude that MMP12 may play a detrimental role in whole-body energy homeostasis and thermogenesis, as it triggers macrophage infiltration, inflammation, and mitochondrial dysfunction in BAT.
Selective targeting of genes regulated by zinc finger proteins in endometriosis and endometrioid adenocarcinoma by zinc niflumato complex with neocuproine Ivana Špaková, Lukáš Smolko, Gabriela Sabolová, Zuzana Badovská, Katarína Kalinová, Corina Madreiter-Sokolowski, Wolfgang F. Graier, Mária Mareková, Janka Vašková, Miroslava Rabajdová Scientific Reports, 2025 Inadequate angiogenesis of endometriotic implants stimulated by the inflammatory microenvironment in the uterine region leads to the development of gynecological diseases, which significantly reduce the fertility and vitality of young women. Angiogenic processes are controlled by factors whose activities are regulated at the gene level by reactive oxygen species (ROS), hypoxia-induced factors (HIFs), and zinc-finger proteins (ZnFs) or posttranscriptionally via non-coding RNAs. The cooperation of these factors is responsible for the manifestation of pathological stimuli in the form of endometriosis of the body of the uterus, ovaries, or peritoneum, from which endometrioid carcinoma can develop. Molecules that can control gene expression by their intercalation to target DNA sequence, such as [Zn(neo)(nif) 2 ], could prevent the hyperactivation of pro-angiogenic pathways (decrease HIF-1α, VEGF-A, TGF-β1, COX2, and ANG2/ANG1), reduce the formation of ROS, and reduce the risk of uterine neoplasticity. The NSAID-metal complex [Zn(neo)(nif) 2 ] shows an ability to intercalate into ZNF3-7 target DNA sequence at a higher rate, which could explain its effect on genes regulated by this transcription factor. In addition, [Zn(neo)(nif) 2 ] affects ROS production and Ca 2+ level, possibly pointing to mitochondrial dysfunction as a potential cause for the described apoptosis.
Enhancing Late-Life Survival and Mobility via Mitohormesis by Reducing Mitochondrial Calcium Levels Doruntina Bresilla, Ines Tawfik, Martin Hirtl, Sonja Gabrijelčič, Julian Ostaku, Fabienne Mossegger, Lia Wurzer, Susanne Lederer, Katarina Kalinova, Ernst Malle, Markus Schosserer, Kim Zarse, Michael Ristow, Corina T. Madreiter‐Sokolowski Aging Cell, 2025 Mitochondrial calcium (Ca2+) homeostasis plays a critical role in aging and cellular fitness. In the search for novel antiaging approaches, we explored how genetic and pharmacological inhibition of mitochondrial Ca2+ uptake influences the lifespan and health of Caenorhabditis elegans. Using live‐cell imaging, we demonstrate that RNA interference‐mediated knockdown of mcu‐1, the nematode ortholog of the mitochondrial Ca2+ uniporter (MCU), reduces mitochondrial Ca2+ levels, thereby extending lifespan and preserving motility during aging, while compromising early‐life survival. This longevity benefit requires intervention before day 14 and coincides with a transient increase in reactive oxygen species (ROS), which activates pathways involving pmk‐1, daf‐16, and skn‐1, orthologs of human p38 mitogen‐activated protein kinase (p38 MAPK), forkhead box O (FOXO), and nuclear factor erythroid 2–related factor 2 (NRF2), respectively. This pathway promotes antioxidant defense mechanisms and preserves mitochondrial structure and function during aging, maintaining larger, more interconnected mitochondria and restoring the oxidized/reduced nicotinamide adenine dinucleotide (NAD+/NADH) ratio and oxygen consumption rates to youthful levels. Pharmacological inhibition of mitochondrial Ca2+ uptake using the MCU inhibitor mitoxantrone mirrors the effects of mcu‐1 knockdown, extending lifespan and improving fitness in aged nematodes. In human foreskin fibroblasts, short‐term mitoxantrone treatment also transiently elevates ROS production and induces enhanced expression and activity of antioxidant defense enzymes, underscoring the translational relevance of findings from nematodes to human cells. Our findings suggest that modulation of mitochondrial Ca2+ uptake induces mitohormesis through ROS‐mediated signaling, promoting improved longevity and healthspan in nematodes, with possible implications for healthy aging in humans.
Targeting enhanced mitochondrial respiration chain activity as a potential therapeutic approach for endometriosis Katarína Kalinová, Benjamin Gottschalk, Martin Hirtl, Julian Ostaku, Sonja Gabrijelčič, Alwin Sokolowski, Ernst Malle, Wolfgang F. Graier, Corina T. Madreiter-Sokolowski Biochimica Et Biophysica Acta Molecular Basis of Disease, 2025 Endometriosis is a chronic condition defined by the presence of endometrial-like tissue outside the uterus. Since endometriotic cells share similarities with cancer cells, including uncontrolled cell growth and invasion, we investigated whether cancer cell-specific rewiring of mitochondrial signaling is also present in endometriotic cells. We utilized the endometriotic cell line 12Z and investigated its mitochondrial function in comparison with the uterine cancer cell line SK-UT-1 and the mammary epithelial cell line hTERT-HME1. We could show that the endometriotic 12Z cells share structural similarities with cancerous SK-UT-1 cells with enhanced colocalization between the endoplasmic reticulum and mitochondria and increased cristae width and density associated with facilitated mitochondrial Ca 2+ uptake. However, an increase in the reduction equivalent yield and oxygen consumption rate was exclusively found in 12Z cells, whereas the reduced ΔΨ m and the reverse mode of F O F 1 -ATP synthase were also detected in SK-UT-1 cells. These features rendered both cell types susceptible to quercetin and oligomycin A treatment. We assume that the complexes of the electron transport chain and the F O F 1 -ATP synthase in reverse mode have a crucial role in maintaining mitochondrial membrane potential and, thereby, mitochondrial integrity of endometriotic 12Z cells. Therefore, targeting the electron transport chain or the reverse mode of F O F 1 -ATP synthase may represent a promising new treatment strategy for endometriosis. • Endometriotic cells share features with cancer cells in mitochondrial and cristae morphology. • Endometriotic cells show increased mitochondrial calcium uptake, reduction equivalent yield, oxygen consumption rate, and mitochondrial ATP production. • Endometriotic cells exhibit an increased reverse activity of F O F 1 -ATP synthase, potentially counteracting mitochondrial membrane potential loss. • Quercetin effectively kills endometriotic and cancer cells while sparing non-cancerous cells. • Targeting the reverse activity of F O F 1 -ATP synthase might offer a new treatment strategy for endometriosis.
A novel super-resolution STED microscopy analysis approach to observe spatial MCU and MICU1 distribution dynamics in cells Martin Hirtl, Benjamin Gottschalk, Olaf A. Bachkoenig, Furkan E. Oflaz, Corina Madreiter-Sokolowski, Morten Andre Høydal, Wolfgang F. Graier Biochimica Et Biophysica Acta Molecular Cell Research, 2025 The uptake of Ca 2+ by mitochondria is an important and tightly controlled process in various tissues. Even small changes in the key proteins involved in this process can lead to significant cellular dysfunction and, ultimately, cell death. In this study, we used stimulated emission depletion (STED) microscopy and developed an unbiased approach to monitor the sub-mitochondrial distribution and dynamics of the mitochondrial calcium uniporter (MCU) and mitochondrial calcium uptake 1 (MICU1) under resting and stimulated conditions. To visualize the inner mitochondrial membrane, the STED-optimized dye called pkMitoRed was used. The study presented herein builds on the previously verified exclusive localization of MICU1 in the intermembrane space, and that MCU moves exclusively laterally along the inner mitochondrial membrane (IMM). We applied a multi-angled arrow histogram to analyze the distribution of proteins within mitochondria, providing a one-dimensional view of protein localization along a defined distance. Combining this with optimal transport colocalization enabled us to further predict submitochondrial protein distribution. Results indicate that in HeLa cells Ca 2+ elevation yielded MCU translocation from the cristae membrane (CM) to the inner boundary membrane (IBM). In AC16 cardiomyocyte cell line, MCU is mainly located at the IBM under resting conditions, and it translocates to the CM upon rising Ca 2+ . Our data describe a novel unbiased super-resolution image analysis approach. Our showcase sheds light on differences in spatial distribution dynamics of MCU in cell lines with different MICU1:MCU abundance. • We developed a novel unbiased super-resolution STED microscopy-based approach to monitor the dynamics of spatial sub-organellar protein distribution in cells • This new approach revealed that MICU1 accumulates at cristae-junction structures • Further, in non-excitable HeLa cells, MCU is in the cristae, while it shuttles out to the inner boundary membrane upon high Ca 2+ levels • Finally, in the excitable AC16 cardiomyocyte cell line, MCU is homogenously located throughout the whole inner mitochondrial membrane, while it is located predominantly within cristae under high Ca 2+ levels
In vitro examination of Piezo1-TRPV4 dynamics: implications for placental endothelial function in normal and preeclamptic pregnancies Hanna H. Allerkamp, Alexander I. Bondarenko, Ines Tawfik, Nilüfer Kamali-Simsek, Monika Horvat Mercnik, Corina T. Madreiter-Sokolowski, Christian Wadsack American Journal of Physiology Cell Physiology, 2025 This study shows Piezo-type mechanosensitive ion channel component 1 (Piezo1) and transient receptor potential cation channel subfamily V member 4 (TRPV4) coexpression and functionality within primary human fetoplacental endothelial cells (fpECs), mediating nitric oxide (NO) production and barrier integrity. In early-onset preeclampsia (EPE), fpEC channel functionality and coregulation are impaired, affecting Ca2+ signaling and endothelial barrier function. Combined channel activation significantly reduces endothelial barrier integrity and increases NO production in EPE. Changes in arachidonic acid metabolism are suggested as a key underlying factor mediating impaired channel functionality in EPE fpECs.
FXR adapts hepatic mitochondrial function to increased substrate oxidation in patients with obesity Katrin Panzitt, Emilian Jungwirth, Lena E. Vosko, Corina T. Madreiter-Sokolowski, Tobias Madl, Ines Tawfik, Hansjörg Habisch, Jelena Krstic, Andreas Prokesch, Robert Karitnig, Robert Sucher, Ceyhun Y. Erdogan, Thomas A. Vallim, Michael Trauner, Peter Fickert, Samer Al-Dury, Antonio Molinaro, David D. Moore, Gerhard G. Thallinger, Hanns-Ulrich Marschall, Martin Wagner Science Translational Medicine, 2025 Metabolic pressure shifts signaling pathways of nuclear receptors, including the bile acid receptor FXR, which are sensitive to nutritional inputs. We performed an FXR ChIP-seq–centered multiomic analysis of liver biopsy samples from individuals with or without obesity, who were treated with either placebo or the FXR agonist obeticholic acid, to define metabolic adaptions of FXR signaling pathways. FXR occupied substantially more DNA binding sites in individuals with obesity, and FXR activation by OCA robustly changed the transcriptional output. Integration of ChIP-seq and RNA-seq data showed that mitochondrial function and substrate oxidation were the top metabolic pathways selectively modulated by FXR activation in individuals with obesity. FXR activation restored compromised substrate oxidation by enhancing β-oxidation and oxidative phosphorylation along with antagonizing ROS production. In line with this, the amount of reduced glutathione in patients with obesity normalized after OCA treatment. In summary, FXR signaling profoundly differs in patients with obesity, consisting of changes in DNA binding profiles and transcriptional programs, which enhance energy substrate utilization in this patient cohort.
Breast cancer cells utilize T3 to trigger proliferation through cellular Ca2+ modulation Ines Tawfik, Katharina Schlick, Julian Ostaku, Doruntina Bresilla, Sonja Gabrijelčič, Benjamin Gottschalk, Alwin Sokolowski, Ernst Malle, Katarina Kalinova, Martin Hirtl, Corina T. Madreiter-Sokolowski Cell Communication and Signaling, 2024 High levels of thyroid hormones are linked to increased risk and advanced stages of breast cancer. Our previous work demonstrated that the biologically active triiodothyronine (T3) facilitates mitochondrial ATP production by upregulating Ca2+ handling proteins, thereby boosting mitochondrial Ca2+ uptake and Krebs cycle activity. In this study, different cell types were utilized to investigate whether T3 activates a Ca2+-induced signaling pathway to boost cancer cell proliferation. Using live-cell imaging, biochemical assays, and molecular profiling, differences in intracellular signaling among MCF7 and MDA-MB-468 breast cancer cells, non-cancerous breast cells hTERT-HME1, and PC3 prostate carcinoma cells, previously found to be insensitive to thyroid hormones in terms of proliferation, were investigated. Our findings revealed that T3 upregulates 1,4,5-trisphosphate receptor 3 via thyroid hormone receptor α. This boosts mitochondrial Ca2+ uptake, reduction equivalent yield, and mitochondrial ATP production, supporting the viability and proliferation of breast cancer cells without affecting non-cancerous hTERT-HME1 or PC3 prostate carcinoma cells. Understanding the interplay between T3 signaling, organellar interaction, and breast cancer metabolism could lead to targeted therapies that exploit cancer cell vulnerabilities. Our findings highlight T3 as a crucial regulator of cancer metabolism, reinforcing its potential as a therapeutic target in breast cancer.
Targeting organ-specific mitochondrial dysfunction to improve biological aging Corina T. Madreiter-Sokolowski, Ursula Hiden, Jelena Krstic, Katrin Panzitt, Martin Wagner, Christian Enzinger, Michael Khalil, Mahmoud Abdellatif, Ernst Malle, Tobias Madl, Elena Osto, Markus Schosserer, Christoph J. Binder, Andrea Olschewski Pharmacology and Therapeutics, 2024
N-acetylaspartate availability is essential for juvenile survival on fat-free diet and determines metabolic health Dina C. Hofer, Gabriel Zirkovits, Helmut J. Pelzmann, Katharina Huber, Ariane R. Pessentheiner, Wenmin Xia, Kyosuke Uno, Toh Miyazaki, Kanta Kon, Hiroshi Tsuneki, Tobias Pendl, Wael Al Zoughbi, Corina T. Madreiter‐Sokolowski, Gert Trausinger, Mahmoud Abdellatif, Gabriele Schoiswohl, Renate Schreiber, Tobias Eisenberg, Christoph Magnes, Simon Sedej, Matthias Eckhardt, Masakiyo Sasahara, Toshiyasu Sasaoka, Atsumi Nitta, Gerald Hoefler, Wolfgang F. Graier, Dagmar Kratky, Johan Auwerx, Juliane G. Bogner‐Strauss FASEB Journal, 2019
Tracking intra- and inter-organelle signaling of mitochondria Corina T. Madreiter‐Sokolowski, Jeta Ramadani‐Muja, Gabriela Ziomek, Sandra Burgstaller, Helmut Bischof, Zhanat Koshenov, Benjamin Gottschalk, Roland Malli, Wolfgang F. Graier FEBS Journal, 2019
Development and Application of Sub-Mitochondrial Targeted Ca2 + Biosensors Markus Waldeck-Weiermair, Benjamin Gottschalk, Corina T. Madreiter-Sokolowski, Jeta Ramadani-Muja, Gabriela Ziomek, Christiane Klec, Sandra Burgstaller, Helmut Bischof, Maria R. Depaoli, Emrah Eroglu, Roland Malli, Wolfgang F. Graier Frontiers in Cellular Neuroscience, 2019
N-acetylaspartate pathway is nutrient responsive and coordinates lipid and energy metabolism in brown adipocytes Katharina Huber, Dina C. Hofer, Sophie Trefely, Helmut J. Pelzmann, Corina Madreiter-Sokolowski, Madalina Duta-Mare, Stefanie Schlager, Gert Trausinger, Sarah Stryeck, Wolfgang F. Graier, Dagmar Kolb, Christoph Magnes, Nathaniel W. Snyder, Andreas Prokesch, Dagmar Kratky, Tobias Madl, Kathryn E. Wellen, Juliane G. Bogner-Strauss Biochimica Et Biophysica Acta Molecular Cell Research, 2019
Cytosolic Aspartate Availability Determines Cell Survival When Glutamine Is Limiting H. Furkan Alkan, Katharina E. Walter, Alba Luengo, Corina T. Madreiter-Sokolowski, Sarah Stryeck, Allison N. Lau, Wael Al-Zoughbi, Caroline A. Lewis, Craig J. Thomas, Gerald Hoefler, Wolfgang F. Graier, Tobias Madl, Matthew G. Vander Heiden, Juliane G. Bogner-Strauss Cell Metabolism, 2018
Critical role of the peroxisomal protein PEX16 in white adipocyte development and lipid homeostasis Dina C. Hofer, Ariane R. Pessentheiner, Helmut J. Pelzmann, Stefanie Schlager, Corina T. Madreiter-Sokolowski, Dagmar Kolb, Thomas O. Eichmann, Gerald Rechberger, Martin Bilban, Wolfgang F. Graier, Dagmar Kratky, Juliane G. Bogner-Strauss Biochimica Et Biophysica Acta Molecular and Cell Biology of Lipids, 2017
Development of novel FP-based probes for live-cell imaging of nitric oxide dynamics Emrah Eroglu, Benjamin Gottschalk, Suphachai Charoensin, Sandra Blass, Helmut Bischof, Rene Rost, Corina T. Madreiter-Sokolowski, Brigitte Pelzmann, Eva Bernhart, Wolfgang Sattler, Seth Hallström, Tadeusz Malinski, Markus Waldeck-Weiermair, Wolfgang F. Graier, Roland Malli Nature Communications, 2016
Deletion of CGI-58 or adipose triglyceride lipase differently affects macrophage function and atherosclerosis Madeleine Goeritzer, Stefanie Schlager, Branislav Radovic, Corina T. Madreiter, Silvia Rainer, Gwynneth Thomas, Caleb C. Lord, Jessica Sacks, Amanda L. Brown, Nemanja Vujic, Sascha Obrowsky, Vinay Sachdev, Dagmar Kolb, Prakash G. Chandak, Wolfgang F. Graier, Wolfgang Sattler, J. Mark Brown, Dagmar Kratky Journal of Lipid Research, 2015
