Biology subjects

Madesh, M.

Publications and source records attributed to Madesh, M..

3 recordsLinked to original sources

bioRxiv2023

Mitochondrial calcium signaling mediated transcriptional regulation of keratin filaments is a critical determinant of melanogenesis

Mitochondria are versatile organelles that regulate several physiological functions. Many mitochondria-controlled processes are driven by mitochondrial Ca2+ signaling. However, role of mitochondrial Ca2+ signaling in melanosome biology remains unknown. Here, we show that pigmentation requires mitochondrial Ca2+ uptake. In vitro gain and loss of function studies demonstrated that Mitochondrial Ca2+ Uniporter (MCU) is crucial for melanogenesis while the MCU rheostats, MCUb and MICU1 negatively control melanogenesis. Zebrafish and mouse models showed that MCU plays a vital role in pigmentation in vivo. Mechanistically, MCU controls activation of transcription factor NFAT2 to induce expression of three keratins (keratin 5, 7 and 8), which we report as positive regulators of melanogenesis. Interestingly, keratin 5 in turn modulates mitochondrial Ca2+ uptake thereby this signaling module acts as a negative feedback loop that fine-tunes both mitochondrial Ca2+ signaling and melanogenesis. Mitoxantrone, an FDA approved drug that inhibits MCU, decreases physiological melanogenesis. Collectively, our data demonstrates a critical role for mitochondrial Ca2+ signaling in vertebrate pigmentation and reveal the therapeutic potential of targeting MCU for clinical management of pigmentary disorders. Given the centrality of mitochondrial Ca2+ signaling and keratin filaments in cellular physiology, this feedback loop may be functional in a variety of other pathophysiological conditions. HighlightsO_LIMCU complex mediated mitochondrial Ca2+ uptake is a novel regulator of vertebrate pigmentation C_LIO_LIKeratin filaments bridge mitochondrial Ca2+ signaling to melanosome biogenesis and maturation C_LIO_LITranscription factor NFAT2 connects mitochondrial Ca2+ dynamics to keratins expression C_LIO_LIMCU-NFAT2-Keratin 5 signaling module generates a negative feedback loop to maintain mitochondrial Ca2+ homeostasis and to ensure optimal melanogenesis C_LIO_LIInhibiting MCU with mitoxantrone, an FDA approved drug, leads to reduction in physiological pigmentation C_LI

cell biology↗

bioRxiv2023

The mitochondrial regulation of smooth muscle cell proliferation in type 2 diabetes

BackgroundType 2 diabetes (T2D) is associated with a strongly increased risk for restenosis after angioplasty driven by proliferation of vascular smooth muscle cells (VSMCs). Here, we sought to determine whether and how mitochondrial dysfunction in T2D drives VSMC proliferation with a focus on ROS and intracellular [Ca2+] that both drive cell proliferation, occur in T2D and are regulated by mitochondrial activity. MethodsUsing a diet-induced mouse model of T2D, the inhibition of the mitochondrial Ca2+/calmodulin-dependent kinase II (mtCaMKII), a regulator of Ca2+ entry via the mitochondrial Ca2+ uniporter selectively in VSMCs, we performed in vivo phenotyping after mechanical injury and established the mechanisms of excessive proliferation in cultured VSMCs. ResultsIn T2D, the inhibition of mtCaMKII reduced both neointima formation after mechanical injury and the proliferation of cultured VSMCs. VSMCs from T2D mice displayed accelerated proliferation, reduced mitochondrial Ca2+ entry and membrane potential with elevated baseline [Ca2+]cyto compared to cells from normoglycemic mice. Accelerated proliferation after PDGF treatment was driven by activation of Erk1/2 and its upstream regulators. Hyperactivation of Erk1/2 was Ca2+-dependent rather than mitochondrial ROS-driven Ca2+-dependent and included the activation of CaMKII in the cytosol. The inhibition of mtCaMKII exaggerated the Ca2+ imbalance by lowering mitochondrial Ca2+ entry and increasing baseline [Ca2+]cyto, further enhancing baseline Erk1/2 activation. With inhibition of mtCaMKII, PDGF treatment had no additional effect on cell proliferation. Inhibition of activated CaMKII in the cytosol decreased excessive Erk1/2 activation and reduced VSMC proliferation. ConclusionsCollectively, our results provide evidence for the molecular mechanisms of enhanced VSMC proliferation after mechanical injury by mitochondrial Ca2+ entry in T2D.

molecular biology↗

bioRxiv2022

The human MRS2 magnesium binding domain is a regulatory feedback switch for channel activity.

Mitochondrial RNA splicing protein 2 (MRS2) forms a major magnesium (Mg2+) entry channel into the matrix. While MRS2 contains two transmembrane domains that constitute a pore, most of the protein resides within the matrix. Yet, the precise structural and functional role of this obtrusive amino terminal domain (NTD) in human MRS2 function is unknown. Here, we show that the MRS2 NTD self-associates into a homodimer, contrasting the pentameric assembly of CorA, an orthologous bacterial channel. Mg2+ and calcium suppress lower and higher order oligomerization of MRS2 NTD, while cobalt has no effect on the NTD but disassembles full-length MRS2. Mutating pinpointed residues mediating Mg2+ binding to the NTD, not only selectively decreases Mg2+ binding affinity [~]7-fold but also abrogates Mg2+ binding-induced changes in secondary, tertiary and quaternary structures. Disruption of NTD Mg2+ binding strikingly potentiates mitochondrial Mg2+ uptake in wild-type and Mrs2 knockout cells. Our work exposes a mechanism for human MRS2 autoregulation by negative feedback from the NTD and identifies a novel gain of function mutant with broad applicability to future Mg2+ signaling research.

biophysics↗