[Endoplasmic reticulum stress response and pathogenesis of non-alcoholic steatohepatitis]

The incidence of chronic liver disease is constantly increasing, owing to the obesity epidemic. Non-alcoholic fatty liver disease (NAFLD) is currently affecting 20-30% of the general population and 75-100% of obese individuals. NAFLD ranges from simple steatosis to damaging non-alcoholic steatohepatitis (NASH), potentially developing into hepatocellular carcinoma. No efficient pharmacological treatment is yet available. During obesity, the hepatic ER stress response can arise from extracellular stress (lipids, glucose, cytokines) and from intracellular stress including lipid buildup in the hepatocyte (steatosis), a hallmark of NAFLD. The chronic activation of the hepatic ER stress response may be a crucial event in the steatosis-NASH transition, triggering cell death, inflammation and accelerating metabolic disorders. We discuss these aspects and we propose that targeting the ER stress response could be effective in treating NAFLD.

[Alpha-1 antitrypsin deficiency: A model of alteration of protein homeostasis or proteostasis]

Chronic obstructive pulmonary disease (COPD) is currently the ninth leading cause of death in France and is predicted to become the third leading cause of worldwide morbidity and mortality by 2020. Risk factors for COPD include exposure to tobacco, dusts and chemicals, asthma and alpha-1 antitrypsin deficiency. This genetic disease, significantly under-diagnosed and under-recognized, affects 1 in 2500 live births and is an important cause of lung and, occasionally, liver disease. Alpha-1 antitrypsin deficiency is a pathology of proteostasis-mediated protein folding and trafficking pathways. To date, there are only palliative therapeutic approaches for the symptoms associated with this hereditary disorder. Therefore, a more detailed understanding is required of the folding and trafficking biology governing alpha-1 antitrypsin biogenesis and its response to drugs. Here, we review the cell biological, biochemical and biophysical properties of alpha-1 antitrypsin and its variants, and we suggest that alpha-1 antitrypsin deficiency is an example of cell autonomous and non-autonomous challenges to proteostasis. Finally, we review emerging strategies that may be used to enhance the proteostasis system and protect the lung from alpha-1 antitrypsin deficiency.

[Alpha-1-antitrypsin deficiency]

Alpha-1-antitrypsin (α1AT) deficiency is a genetic disorder that manifests as pulmonary emphysema and liver cirrhosis. α1AT deficiency is the most common genetic cause of liver disease in children and also an underappreciated cause of liver disease in adults. The prevalence in the general population in Western Europe is approximately 1 in 2,000. The most common and severe deficiency allele is the Z variant (two alleles mutated). This variant is characterized by the accumulation of Z-α1AT polymers in the endoplasmic reticulum of hepatocytes leading to cell death and to a severe reduction of α1AT in the serum. The latter results in a loss of its antiprotease activity and its ability to protect lung tissue. Thus far, there are only very limited therapeutic options in α1AT deficiency. A more detailed understanding of the biology governing α1AT biogenesis is required in order to identify new pharmacological agents and biomarkers. This review will present current knowledge on α1AT deficiency and focus on recent discoveries and new strategies in the treatment of this disease.

[A uNick protein]

Nck is an adaptor protein composed of three N-terminal Src Homology (SH) 3 domains followed by a unique C‑terminal SH2 domain. Like other SH2/SH3 domains-containing adaptor proteins, Nck mediates signal transduction from activated cell surface receptors by directing the flow of information to elicit properly orchestrated cell responses. In this way, Nck appears to be unique in its contribution to a wide variety of cellular processes. Moreover, in addition to the typical signal/pY-SH2/SH3-effectors mode of signaling, Nck also transduces signals through an inverse mode of -signaling (signal-SH3/SH2-pY/effectors) and from various cell compartments. Since Nck contributes to important morphogenic and mitogenic processes, deregulated expression of Nck could be detrimental to cellular homeostasis. In agreement, Nck expression has been found upregulated in numerous types of cancer. In this paper we delineate the main molecular -signaling -complexes associated with Nck, focusing on those involved in cancer progression.

[Involvement of endoplasmic reticulum stress in solid organ transplantation]

Endoplasmic reticulum (ER) stress is a situation caused by the accumulation of unfolded proteins in the endoplasmic reticulum, triggering an evolutionary conserved adaptive response termed the unfolded protein response. When adaptation fails, excessive and prolonged ER stress triggers cell suicide. Important roles for ER-initiated cell death pathways have been recognized for several diseases, including diabetes, hypoxia, ischemia/reperfusion injury, neurodegenerative and heart diseases. The implication of the ER stress is not well recognized in solid organ transplantation, but increasing evidence suggests its implication in mediating allograft injury. The purpose of this review is to summarize the mechanisms of ER stress and to discuss its implication during tissue injury in solid organ transplantation. The possible implications of the ER stress in the modifications of cell functional properties and phenotypic changes are also discussed beyond the scope of adaptation and cell death. Increasing the understanding of the cellular and molecular mechanisms of acute and chronic allograft damages could lead to the development of new biomarkers and to the discovery of new therapeutic strategies to prevent the initiation of graft dysfunction or to promote the tissue regeneration after injury.