Cellular compartment

About: Cellular compartment is a research topic. Over the lifetime, 1082 publications have been published within this topic receiving 53794 citations. The topic is also known as: cell compartmentation.

Modulation of Photorespiratory Enzymes by Oxidative and Photo-Oxidative Stress Induced by Menadione in Leaves of Pea (Pisum sativum).

Abstract: Photorespiration, an essential component of plant metabolism, is concerted across four subcellular compartments, namely, chloroplast, peroxisome, mitochondrion, and the cytoplasm. It is unclear how the pathway located in different subcellular compartments respond to stress occurring exclusively in one of those. We attempted to assess the inter-organelle interaction during the photorespiratory pathway. For that purpose, we induced oxidative stress by menadione (MD) in mitochondria and photo-oxidative stress (high light) in chloroplasts. Subsequently, we examined the changes in selected photorespiratory enzymes, known to be located in other subcellular compartments. The presence of MD upregulated the transcript and protein levels of five chosen photorespiratory enzymes in both normal and high light. Peroxisomal glycolate oxidase and catalase activities increased by 50% and 25%, respectively, while chloroplastic glycerate kinase and phosphoglycolate phosphatase increased by ~30%. The effect of MD was maximum in high light, indicating photo-oxidative stress was an influential factor to regulate photorespiration. Oxidative stress created in mitochondria caused a coordinative upregulation of photorespiration in other organelles. We provided evidence that reactive oxygen species are important signals for inter-organelle communication during photorespiration. Thus, MD can be a valuable tool to modulate the redox state in plant cells to study the metabolic consequences across membranes.

Effects of adrenaline on a compartment of slowly-exchangeable calcium in the perfused rat heart

Abstract: The effects of adrenaline on kinetically-distinct compartments of exchangeable calcium in the spontaneously-beating perfused rat heart were investigated under steady-state conditions using a 45Ca2+ outflow technique together with a nonlinear least-squares curve fitting procedure and 51Cr-EDTA to monitor the loss of freely-diffusible Ca2+ from the extracellular space. In addition to Ca2+ distributed in the vascular (compartment 1) and interstitial (compartment 2) spaces, the minimum number of kinetically-distinct compartments of cellular exchangeable Ca2+ (which include Ca2+ bound to extracellular sites on the sarcolemma) required to fit the data (compartments 3,4 and 5) was three. A system in which cellular compartment 3 is linked to the vascular space and compartments 4 and 5 are linked to the interstitial space was consistent with the data. For hearts perfused under control conditions, the fractional transfer rates for Ca2+ outflow from cellular compartments 3, 4 and 5 were 0.70, 0.11 and 0.017 min−1, respectively. Adrenaline increased the quantity of exchangeable Ca2+ in compartment 5 and decreased that present in the compartment 4. Evidence that compartment 5 includes mitochondrial exchangeable Ca2+ is discussed. It is concluded that one of the actions of adrenaline on the heart is to increase the quantity of exchangeable Ca2+ in the mitochondria.

Study of the Cellular Role of GRP78/BiP mono-ADP-ribosylation in UPR and Cancer

Abstract: Mono-ADP-ribosylation is a reversible post-translational protein modification that modulates the function of proteins involved in different cellular processes, including signal transduction, protein transport, transcription, cell cycle regulation, DNA (deoxyribonucleic acid) repair and apoptosis. In mammals, mono-ADPribosylation is catalyzed by three different classes of enzymes: ARTCs, ARTDs, and members of the sirtuin family. In the present study, hARTC1-mediated mono-ADP-ribosylation was investigated in terms of the cellular compartments involved, target(s) and roles. The collected results demonstrated that hARTC1 protein and enzymatic activity is mainly localized to the endoplasmic reticulum (ER), in contrast to other ARTCs, which are either typically GPI-anchored enzymes in the plasma membrane, or secreted enzymes. Previous studies in my laboratory demonstrated that a protein macro domain was useful for the study of APD-ribosylation. The data reported here indicate, for the first time, that the macro domain can be used for immunofluorescence, allowing visualization of ADP-ribosylated proteins in intact cells, and in far-Western Blotting, allowing the detection of specific ADPribosylated targets. These methodologies were employed to demonstrate that the ER-localized chaperone, GRP78/BiP, was a prime target of hARTC1. A doubly mutated hARTC1 mutant was designed, and used as a specific control for hARTC1 expression. The mutant enzyme localized to the ER, but did not catalyze GRP78/BiP ADP-ribosylation. The demonstration that GRP78/BiP was mono-ADP-ribosylated by hARTC1 suggested that hARTC1 could be a key regulator of GRP78/BiP-mediated functions. Consistent with the key role of GRP78/BiP in the ER stress response, it was found that hARTC1 was activated during short-term cell treatment with ER stressors, resulting in acute GRP78/BiP ADP-ribosylation. However, the monoADP-ribosylation of the chaperone did not trigger an unfolded protein response. Recently, hARTC1 has been associated with cancer, suggesting a possible role in cell proliferation. In line with these findings, the results presented here demonstrated that hARTC1 over-expression inhibited cell proliferation.