Inter-organellar communication is emerging as one of the most crucial regulators of cellular physiology. One of the key regulators of inter-organellar communication is Mitofusin-2 (MFN2). MFN2 is also involved in mediating mitochondrial fusion–fission dynamics. Further, it facilitates mitochondrial crosstalk with the endoplasmic reticulum, lysosomes and melanosomes, which are lysosome-related organelles specialized in melanin synthesis within melanocytes. However, the role of MFN2 in regulating melanocyte-specific cellular function, i.e., melanogenesis, remains poorly understood. Here, using a B16 mouse melanoma cell line and primary human melanocytes, we report that MFN2 negatively regulates melanogenesis. Both the transient and stable knockdown of MFN2 leads to enhanced melanogenesis, which is associated with an increase in the number of mature (stage III and IV) melanosomes and the augmented expression of key melanogenic enzymes. Further, the ectopic expression of MFN2 in MFN2-silenced cells leads to the complete rescue of the phenotype at the cellular and molecular levels. Mechanistically, MFN2-silencing elevates mitochondrial reactive-oxygen-species (ROS) levels which in turn increases melanogenesis. ROS quenching with the antioxidant N-acetyl cysteine (NAC) reverses the MFN2-knockdown-mediated increase in melanogenesis. Moreover, MFN2 expression is significantly lower in the darkly pigmented primary human melanocytes in comparison to lightly pigmented melanocytes, highlighting a potential contribution of lower MFN2 levels to higher physiological pigmentation. Taken together, our work establishes MFN2 as a novel negative regulator of melanogenesis.
Store operated Ca2+ entry (SOCE) mediated by Orai1/2/3 channels is a highly regulated and ubiquitous Ca2+ influx pathway. Although the role of Orai1 channels is well studied, the significance of Orai2/3 channels is still emerging in nature. In this study, we performed extensive bioinformatic analysis of publicly available datasets and observed that Orai3 expression is inversely associated with the mean survival time of PC patients. Orai3 expression analysis in a battery of PC cell lines corroborated its differential expression profile. We then carried out thorough Ca2+ imaging experiments in six PC cell lines and found that Orai3 forms a functional SOCE channel in PC cells. Our in vitro functional assays show that Orai3 regulates PC cell cycle progression, apoptosis and migration. Most importantly, our in vivo xenograft studies demonstrate a critical role of Orai3 in PC tumor growth and secondary metastasis. Mechanistically, Orai3 controls G1 phase progression, matrix metalloproteinase expression and epithelial-mesenchymal transition in PC cells. Taken together, this study for the first-time reports that Orai3 drives aggressive phenotypes of PC cells, i.e., migration in vitro and metastasis in vivo. Considering that Orai3 overexpression leads to poor prognosis in PC patients, it appears to be a highly attractive therapeutic target.
Present study deals with the structure and development of conducting elements in the nine orders of acrocarpous mosses. The significance of conducting tissues in mosses in relation to their habitat conditions, growth forms and leaf cell patterns has been discussed. Features of cells in different portions of the stem and the laminal cell patterns and costa are taken into consideration. Although water-conducting cells are unspecialized in mosses, yet the study shows that they seem to play a vital role in the conduction and provide additional criteria for the distinction of taxa. Four categories have been determined as (i) Acrocarpous mosses with a distinct thick-walled conducting strand (6-7 layered) as hydrome which is surrounded by patches of leptoids. Cortex consists of thick walled cells (6-10 layered). Costa has stereidal cells and well developed conducting elements in leaf, example Polytrichum (ii) Acrocarps with thick-walled, narrow, elongated conducting strand (4-5 layered), cells angular in the cortex (6-8 layered). Leaf cells are rectangular, irregular and porous with incrassate walls, example Dicranum (iii) Acrocarps with conducting tissue (2-5 layered) stereidal, thick walled or thin walled varying in the course of development. Leaf cells are mutipapillate, rounded-quadrate, costa is present, examples Hyophila, Philonotis and (iv) Epiphytic pleurocarps with conducting cells rudimentary, thickened, scattered (2-4 layers) and parenchymatous, cortical cells (2-3 layered) thick walled. Leaf cells are small, rounded or linear and papillate, costa may be present or absent, example Leucodon. The study would constitute a formidable task, especially if intraspecific structural variability is considered. It serves a model system in the eco-physiological aspects.
Pancreatic cancer (PC) is one of the most lethal forms of cancers with 5-year mean survival rate of less than 10%. Most of the PC associated deaths are due to metastasis to secondary sites. Calcium (Ca2+) signaling plays a critical role in regulating hallmarks of cancer progression including cell proliferation, migration and apoptotic resistance. Store operated Ca2+ entry (SOCE) mediated by Orai1/2/3 channels is a highly regulated and ubiquitous pathway responsible for Ca2+ influx into non-excitable cells. In this study, we performed extensive bioinformatic analysis of publicly available datasets and observed that Orai3 expression is inversely associated with the mean survival time of PC patients. Orai3 expression analysis in a battery of PC cell lines corroborated its differential expression profile. We then carried out thorough Ca2+ imaging experiments in 6 PC cell lines and found that Orai3 forms a functional SOCE in PC cells. Our in vitro functional assays show that Orai3 regulates PC cell cycle progression, apoptosis and migration. Most importantly, our in vivo xenograft studies demonstrate a critical role of Orai3 in PC tumor growth and secondary metastasis. Mechanistically, Orai3 controls G1 phase progression, matrix metalloproteinase expression and epithelial-mesenchymal transition in PC cells. Taken together, this study for the first time reports that Orai3 drives aggressive phenotypes of PC cells i.e. migration in vitro and metastasis in vivo. Considering that Orai3 expression is inversely associated with the PC patients survival time, it appears to be a highly attractive therapeutic target.
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