From cell signalling to cell death: endoplasmic reticulum-mitochondria calcium transfer and its remodelling for cancer cell survival

The tight interplay between endoplasmic reticulum (ER) and mitochondria is a key determinant of cell function and survival through the control of intracellular calcium (Ca2+) signalling. The physical platform for the association between the ER and mitochondria is a domain of the ER called the “mitochondria-associated membranes” (MAMs). MAMs are crucial for highly efficient transmission of Ca2+ from the ER to mitochondria, thus controlling fundamental processes involved in energy production and also determining cell fate by triggering or preventing apoptosis. In particular, we show that: i) despite different roles in cell survival, all three isoforms of the outer mitochondrial membrane protein voltage-dependent anion channels (VDAC) are equivalent in allowing mitochondrial Ca2+ loading upon agonist stimulation, vice versa VDAC1, by selectively interacting with the inositol trisphosphate receptors (IP3Rs) - an interaction that is further strengthened by apoptotic stimuli - is preferentially involved in the transmission of the low-amplitude apoptotic Ca2+ signals to mitochondria, highlighting a non-redundant molecular route for transferring Ca2+ signals to mitochondria in apoptosis; ii) the promyelocytic leukemia (PML) tumor suppressor exerts its extranuclear proapoptotic action by its unexpected and fundamental role at MAMs, where PML was found in protein complexes with the type 3 IP3R, the protein kinase Akt and the phosphatase PP2a, which are essential for Akt- and PP2a-dependent modulation of IP3R phosphorylation and in turn for IP3R-mediated Ca2+ release from ER; iii) the PTEN (phosphatase and tensin homolog deleted on chromosome 10) tumor suppressor localizes at the ER and MAMs, and ER-localized PTEN is specifically involved in increasing both Ca2+ transfer from the ER to mitochondria and cell sensitivity to Ca2+-mediated apoptosis. The improved knowledge of the functioning of proteins involved in regulating Ca2+ signalling may reveal novel unexplored pharmacological targets, and help in treating cancer as well as other pathologies

Mitochondria-Ros Crosstalk in the Control of Cell Death and Aging

Reactive oxygen species (ROS) are highly reactive molecules, mainly generated inside mitochondria that can oxidize DNA, proteins, and lipids. At physiological levels, ROS function as “redox messengers” in intracellular signalling and regulation, whereas excess ROS induce cell death by promoting the intrinsic apoptotic pathway. Recent work has pointed to a further role of ROS in activation of autophagy and their importance in the regulation of aging. This review will focus on mitochondria as producers and targets of ROS and will summarize different proteins that modulate the redox state of the cell. Moreover, the involvement of ROS and mitochondria in different molecular pathways controlling lifespan will be reported, pointing out the role of ROS as a “balance of power,” directing the cell towards life or death

Transglutaminase 2 Contributes to Apoptosis Induction in Jurkat T Cells by Modulating Ca(2+) Homeostasis via Cross-Linking RAP1GDS1

BACKGROUND: Transglutaminase 2 (TG2) is a protein cross-linking enzyme known to be associated with the in vivo apoptosis program of T cells. However, its role in the T cell apoptosis program was not investigated yet. RESULTS: Here we report that timed overexpression of both the wild type (wt) and the cross-linking mutant of TG2 induced apoptosis in Jurkat T cells, the wt being more effective. Part of TG2 colocalised with mitochondria. WtTG2-induced apoptosis was characterized by enhanced mitochondrial Ca(2+) uptake. Ca(2+)-activated wtTG2 cross-linked RAP1, GTP-GDP dissociation stimulator 1, an unusual guanine exchange factor acting on various small GTPases, to induce a yet uncharacterized signaling pathway that was able to promote the Ca(2+) release from the endoplasmic reticulum via both Ins3P and ryanodine sensitive receptors leading to a consequently enhanced mitochondrial Ca(2+)uptake. CONCLUSIONS: Our data indicate that TG2 might act as a Ca(2+) sensor to amplify endoplasmic reticulum-derived Ca(2+) signals to enhance mitochondria Ca(2+) uptake. Since enhanced mitochondrial Ca(2+) levels were previously shown to sensitize mitochondria for various apoptotic signals, our data demonstrate a novel mechanism through which TG2 can contribute to the induction of apoptosis in certain cell types. Since, as compared to knock out cells, physiological levels of TG2 affected Ca(2+) signals in mouse embryonic fibroblasts similar to Jurkat cells, our data might indicate a more general role of TG2 in the regulation of mitochondrial Ca(2+) homeostasis

Oxidative Stress in Cardiovascular Diseases and Obesity: Role of p66Shc and Protein Kinase C

Reactive oxygen species (ROS) are a byproduct of the normal metabolism of oxygen and have important roles in cell signalling and homeostasis. An imbalance between ROS production and the cellular antioxidant defence system leads to oxidative stress. Environmental factors and genetic interactions play key roles in oxidative stress mediated pathologies. In this paper, we focus on cardiovascular diseases and obesity, disorders strongly related to each other; in which oxidative stress plays a fundamental role. We provide evidence of the key role played by p66Shc protein and protein kinase C (PKC) in these pathologies by their intracellular regulation of redox balance and oxidative stress levels. Additionally, we discuss possible therapeutic strategies aimed at attenuating the oxidative damage in these diseases

Biological Mechanisms and Clinical Significance of BAP1 Mutations in Human Cancer

Among more than 200 -mutant families affected by the "BAP1 cancer syndrome," nearly all individuals inheriting a mutant allele developed one or more malignancies during their lifetime, mostly uveal and cutaneous melanoma, mesothelioma, and clear-cell renal cell carcinoma. These cancer types are also those that, when they occur sporadically, are more likely to carry somatic biallelic mutations. Mechanistic studies revealed that the tumor suppressor function of BAP1 is linked to its dual activity in the nucleus, where it is implicated in a variety of processes including DNA repair and transcription, and in the cytoplasm, where it regulates cell death and mitochondrial metabolism. BAP1 activity in tumor suppression is cell type- and context-dependent. BAP1 has emerged as a critical tumor suppressor across multiple cancer types, predisposing to tumor development when mutated in the germline as well as somatically. Moreover, has emerged as a key regulator of gene-environment interaction.

Protein Kinases and Phosphatases in the Control of Cell Fate

Protein phosphorylation controls many aspects of cell fate and is often deregulated in pathological conditions. Several recent findings have provided an intriguing insight into the spatial regulation of protein phosphorylation across different subcellular compartments and how this can be finely orchestrated by specific kinases and phosphatases. In this review, the focus will be placed on (i) the phosphoinositide 3-kinase (PI3K) pathway, specifically on the kinases Akt and mTOR and on the phosphatases PP2a and PTEN, and on (ii) the PKC family of serine/threonine kinases. We will look at general aspects of cell physiology controlled by these kinases and phosphatases, highlighting the signalling pathways that drive cell division, proliferation, and apoptosis

REDOX CONTROL OF PROTEIN KINASE C: CELL AND DISEASE SPECIFIC ASPECTS.

none12Hormones, growth factors, electrical stimulation, and cell-cell interactions regulate numerous cellular processes by altering the levels of second messengers, thus influencing biochemical reactions inside the cells. The Protein Kinase C family (PKCs) is a group of serine/threonine kinases that are dependent on calcium (Ca2+), diacylglycerol, and phospholipids. Signalling pathways that induce variations on the levels of PKC activators have been implicated in the regulation of diverse cellular functions and, in turn, PKCs are key regulators of a plethora of cellular processes, including proliferation, differentiation, and tumorigenesis. Importantly, PKCs contain regions, both in the N-terminal regulatory domain and in the C-terminal catalytic domain, that are susceptible to redox modifications. In several pathophysiological conditions when the balance between oxidants, anti-oxidants and alkylants is compromised, cells undergo redox stress. PKCs are cell-signalling proteins that are particularly sensitive to redox stress because modification of their redox-sensitive regions interferes with their activity and, thus, with their biological effects. In this review, we summarize the involvement of PKCs in health and disease and the importance of redox signalling in the regulation of this family of kinases.noneGiorgi C; Agnoletto C; Baldini C; Bononi A; Bonora M; Marchi S; Missiroli S; Patergnani S; Poletti F; Rimessi A; Zavan B; Pinton PGiorgi, Carlotta; Agnoletto, Chiara; Baldini, Claudio; Bononi, Angela; Bonora, Massimo; Marchi, Saverio; Missiroli, Sonia; Patergnani, Simone; Poletti, Federica; Rimessi, Alessandro; Zavan, B; Pinton, Paol

ATP synthesis and storage

Since 1929, when it was discovered that ATP is a substrate for muscle contraction, the knowledge about this purine nucleotide has been greatly expanded. Many aspects of cell metabolism revolve around ATP production and consumption. It is important to understand the concepts of glucose and oxygen consumption in aerobic and anaerobic life and to link bioenergetics with the vast amount of reactions occurring within cells. ATP is universally seen as the energy exchange factor that connects anabolism and catabolism but also fuels processes such as motile contraction, phosphorylations, and active transport. It is also a signalling molecule in the purinergic signalling mechanisms. In this review, we will discuss all the main mechanisms of ATP production linked to ADP phosphorylation as well the regulation of these mechanisms during stress conditions and in connection with calcium signalling events. Recent advances regarding ATP storage and its special significance for purinergic signalling will also be reviewed

Mitochondrial Ca2+and apoptosis

none12noneGiorgi, Carlotta; Baldassari, Federica; Bononi, Angela; Bonora, Massimo; De Marchi, Elena; Marchi, Saverio; Missiroli, Sonia; Patergnani, Simone; Rimessi, Alessandro; Suski, Jan M.; Wieckowski, Mariusz R.; Pinton, Paolo*Giorgi, Carlotta; Baldassari, Federica; Bononi, Angela; Bonora, Massimo; De Marchi, Elena; Marchi, Saverio; Missiroli, Sonia; Patergnani, Simone; Rimessi, Alessandro; Suski, Jan M.; Wieckowski, Mariusz R.; Pinton, Paol