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Ischemic Inhibition of Calcium Slow Current in the Heart
Published in Samuel Sideman, Rafael Beyar, Analysis and Simulation of the Cardiac System — Ischemia, 2020
Therefore, it appears that calmodulin also plays a potentiating role in the regulation of the myocardial Ca2+ slow channels. This effect may be mediated by the Ca2+-calmodulin protein kinase and phosphorylation of a protein that affects the functioning of the slow channel (Figure 10). It is possible that a regulatory protein associated with the slow channel, when phosphorylated, acts to make that slow channel become available for voltage activation, i.e., a protein associated with the slow channel may be phosphorylated by the Ca2+-calmodulin-dependent protein kinase, which may, in some manner, potentiate the effects of cAMP-dependent phosphorylation of the slow channel. Thus, it appears that maximal activation of the slow channels requires two separate phosphorylation steps. These may be on the same protein (Figure 10) or on two separate proteins (i.e., two stimulatory regulatory components).
Receptor-Ligand Interactions that are Disaproportionate With Their Physiological Effects
Published in John C. Matthews, Fundamentals of Receptor, Enzyme, and Transport Kinetics, 2017
Calmodulin is a cytoplasmic protein that functions to bind calcium. The calcium-calmodulin complex, in turn, binds to various enzymes and proteins in the cell to alter their activities, thereby producing the physiological effect. Each calmodulin molecule has four binding sites for calcium, which, like hemoglobin, exhibit cooperativity. In the calcium-calmodulin system the calcium enters the cell cytoplasm from outside the cell through calcium channels or it is released from stores in the endoplasmic reticulum. The calmodulin, in its role in signal transduction, needs to be able to respond in a nearly all-or-none fashion to calcium concentration changes. It must go from a near zero binding site occupancy to near fully occupied binding sites over a very narrow concentration range when calcium enters the cytoplasm. The calmodulin must then go from near fully occupied to near fully unoccupied over the same very narrow concentration range as the calcium is pumped out of the cytoplasm. The cooperativity of its interaction with calcium permits calmodulin to function in the manner required.
Role of Calcium Ions and the Phospholipids in the Prolactin Regulation of Its Target Cells
Published in James A. Rillema, Actions of Prolactin on Molecular Processes, 1987
Calmodulin is a cellular protein which combines with calcium and reduces the calcium ion concentration required to activate certain calcium-dependent enzymes.44–46 The fact that calmodulin is contained in mammary tissues was suggested in a report by Pizarro et al.47 These investigators reported that a protein derived from lactating rat mammary tissues functions in concert with 10 μM calcium to activate cyclic AMP- and cyclic GMP-dependent phosphodiesterase; this protein was identified as calmodulin by showing that trifluoperazine abolished its activity. Calmodulin content was shown to increase about twofold in rat mammary tissues at the time of parturition and its concentration remained the same through 20 days of lactation. In a more recent study, Mullaney and Clegg48 reported the existence of a specific calcium-calmodulin-dependent cyclic GMP phosphodiesterase obtained from mammary tissues of rats in midlactation. It thus seems clear that calmodulin does exist in mammary tissues. It is also likely that calmodulin activates more enzymes in mammary cells other than just the cyclic nucleotide phosphodiesterases. In addition, if prolactin does act on cells to increase intracellular calcium ion concentrations, at least certain of the actions of prolactin may be carried out by the activation of calcium-calmodulin-dependent enzymes.
The role of synaptic biomarkers in the spectrum of neurodegenerative diseases
Published in Expert Review of Proteomics, 2020
Sonia Mazzucchi, Giovanni Palermo, Nicole Campese, Alessandro Galgani, Alessandra Della Vecchia, Andrea Vergallo, Gabriele Siciliano, Roberto Ceravolo, Harald Hampel, Filippo Baldacci
Ng is a 78 aa neuron-specific post-synaptic somato-dendritic protein. It is one of the most abundant calmodulin-binding proteins and is mainly expressed by excitatory neurons of the cerebral cortex and hippocampus. High levels can be measured in amygdala, caudate, and putamen, whereas it is poorly expressed or absent in other brain regions as the thalamus, cerebellum, brainstem, and the spinal cord [5]. The protein can be found in neurons but is not expressed by glial cells. Ng regulates synaptic activity, mainly LTP, through its binding to calmodulin that is increased in the presence of low calcium concentrations and inhibited by large calcium amounts. In animal models, Ng overexpression demonstrated to enhance LTP and improve cognitive performances, whereas in Ng knockout mice memory deficits were reported, probably due to an impairment or even a block of LTP [8]. Furthermore, preclinical studies highlighted an age-dependent reduction of Ng mRNA in several brain regions, including the hippocampus [28].
Phillygenin exhibits anti-inflammatory activity through modulating multiple cellular behaviors of mouse lymphocytes
Published in Immunopharmacology and Immunotoxicology, 2019
Bingyuan Du, Li Zhang, Ying Sun, Guimin Zhang, Jingchun Yao, Mingmin Jiang, Lihong Pan, Chenghong Sun
We showed in this study that PHI is able to suppress Con A-induced lymphocytes proliferation via G0/G1 cell cycle arrest. There was increasing evidence indicated that regulating cell cycle played an important role in inflammatory injury [18]. Ca2+ is an essential second messenger that regulates diverse cellular processes, and many calcium-related proteins involved in regulation of cell cycle progress. Calmodulin (CaM), the high affinity calcium binding protein, is important to regulate cell cycle progression, and the Ca2+/CaM complex initiates a plethora of signaling cascades that culminate in alteration of cellular functions [19]. Thus, Ca2+ is a structurally and functionally important factor for correct folding of Con A to form a tertiary structure [20]. As such, the relevant Ca2+ results shown in this study were supportive for the cell cycle G0/G1 phase arrest. Meanwhile, the western blotting results indicated that PHI inhibited the Con A-induced overexpression of cyclin D1 and cyclin E (G0/G1 phase cyclins required for S transition), which was consistent with the flow cytometry plus PI-staining results.