Ca2+ Microdomains, Calcineurin and the Regulation of Gene Transcription

Ca2+ ions function as second messengers regulating many intracellular events, including neurotransmitter release, exocytosis, muscle contraction, metabolism and gene transcription. Cells of a multicellular organism express a variety of cell-surface receptors and channels that trigger an increase of the intracellular Ca2+ concentration upon stimulation. The elevated Ca2+ concentration is not uniformly distributed within the cytoplasm but is organized in subcellular microdomains with high and low concentrations of Ca2+ at different locations in the cell. Ca2+ ions are stored and released by intracellular organelles that change the concentration and distribution of Ca2+ ions. A major function of the rise in intracellular Ca2+ is the change of the genetic expression pattern of the cell via the activation of Ca2+-responsive transcription factors. It has been proposed that Ca2+-responsive transcription factors are differently affected by a rise in cytoplasmic versus nuclear Ca2+. Moreover, it has been suggested that the mode of entry determines whether an influx of Ca2+ leads to the stimulation of gene transcription. A rise in cytoplasmic Ca2+ induces an intracellular signaling cascade, involving the activation of the Ca2+/calmodulin-dependent protein phosphatase calcineurin and various protein kinases (protein kinase C, extracellular signal-regulated protein kinase, Ca2+/calmodulin-dependent protein kinases). In this review article, we discuss the concept of gene regulation via elevated Ca2+ concentration in the cytoplasm and the nucleus, the role of Ca2+ entry and the role of enzymes as signal transducers. We give particular emphasis to the regulation of gene transcription by calcineurin, linking protein dephosphorylation with Ca2+ signaling and gene expression.

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Effects of endothelin on rat renal proximal tubule Na(+)-Pi cotransport and Na+/H+ exchange

AJP Renal Physiology ◽

10.1152/ajprenal.1994.266.4.f658 ◽

1994 ◽

Vol 266 (4) ◽

pp. F658-F666 ◽

Cited By ~ 7

Author(s):

J. Guntupalli ◽

T. D. DuBose

Keyword(s):

Protein Kinase ◽

Proximal Tubule ◽

Collecting Duct ◽

Second Messengers ◽

Indirect Evidence ◽

Low Concentrations ◽

Proximal Tubular ◽

Dependent Protein ◽

Medullary Collecting Duct

Endothelin (ET), a powerful vasoconstrictive peptide, is distributed ubiquitously in various organs, including the vascular endothelium and tubules of the kidney. Although localized more abundantly to the glomerulus and inner medullary collecting duct, ET receptors have been identified in the proximal tubule. The possible effects of ET on proximal tubule transport and the potential role of second messengers in this process have not been described fully. To define the role of ET in proximal tubule transport, renal cortical slices were incubated for 3 min in the presence of various concentrations of ET. Incubation with low concentrations of ET-1 (1 x 10(-9) to 1 x 10(-11) M) within the physiological range stimulated both Na(+)-Pi cotransport and Na+/H+ exchange. Pretreatment with staurosporine (0.6 microM) for 25 min abolished completely the ET-induced effects on Na(+)-Pi cotransport and Na+/H+ exchange. Similarly, preincubation with phorbol ester 12-O-tetradecanoylphorbol-13-acetate (200 nM) also abolished the effects of ET on these transporters. Incubation with ET decreased significantly intracellular adenosine 3',5'-cyclic monophosphate (cAMP). Intravenous administration of pertussis toxin for 2 days prevented the ET-induced decrease in cAMP and abolished the stimulatory effects of ET on Na(+)-Pi cotransport and Na+/H+ exchange. These findings provide indirect evidence that ET participates in the regulation of proximal tubular Pi and bicarbonate homeostasis. These effects of ET are mediated by activation of protein kinase C and cAMP-dependent protein kinase A.

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Mutation of a kinase allosteric node uncouples dynamics linked to phosphotransfer

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1620667114 ◽

2017 ◽

Vol 114 (6) ◽

pp. E931-E940 ◽

Cited By ~ 21

Author(s):

Lalima G. Ahuja ◽

Alexandr P. Kornev ◽

Christopher L. McClendon ◽

Gianluigi Veglia ◽

Susan S. Taylor

Keyword(s):

Protein Kinase ◽

Protein Kinases ◽

Dynamic Properties ◽

Dynamic Structure ◽

Kinase Domain ◽

Catalytic Function ◽

Dependent Protein ◽

Health And Disease ◽

Biochemical Measurements

The expertise of protein kinases lies in their dynamic structure, wherein they are able to modulate cellular signaling by their phosphotransferase activity. Only a few hundreds of protein kinases regulate key processes in human cells, and protein kinases play a pivotal role in health and disease. The present study dwells on understanding the working of the protein kinase-molecular switch as an allosteric network of “communities” composed of congruently dynamic residues that make up the protein kinase core. Girvan–Newman algorithm-based community maps of the kinase domain of cAMP-dependent protein kinase A allow for a molecular explanation for the role of protein conformational entropy in its catalytic cycle. The community map of a mutant, Y204A, is analyzed vis-à-vis the wild-type protein to study the perturbations in its dynamic profile such that it interferes with transfer of the γ-phosphate to a protein substrate. Conventional biochemical measurements are used to ascertain the effect of these dynamic perturbations on the kinetic profiles of both proteins. These studies pave the way for understanding how mutations far from the kinase active site can alter its dynamic properties and catalytic function even when major structural perturbations are not obvious from static crystal structures.

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Invited Review: Regulation of myosin phosphorylation in smooth muscle

Journal of Applied Physiology ◽

10.1152/jappl.2001.91.1.497 ◽

2001 ◽

Vol 91 (1) ◽

pp. 497-503 ◽

Cited By ~ 211

Author(s):

Gabriele Pfitzer

Keyword(s):

Smooth Muscle ◽

Protein Kinase ◽

Protein Kinases ◽

Intracellular Signaling ◽

Muscle Tone ◽

Force Production ◽

Regulatory Subunit ◽

Regulatory Light Chains ◽

Smooth Muscle Tone ◽

Dependent Protein

Phosphorylation of the regulatory light chains of myosin II (rMLC) by the Ca2+/calmodulin-dependent myosin light-chain kinase (MLCK) and dephosphorylation by a type 1 phosphatase (MLCP), which is targeted to myosin by a regulatory subunit (MYPT1), are the predominant mechanisms of regulation of smooth muscle tone. The activities of both enzymes are modulated by several protein kinases. MLCK is inhibited by the Ca2+/calmodulin-dependent protein kinase II, whereas the activity of MLCP is increased by cGMP and perhaps also cAMP-dependent protein kinases. In either case, this results in a decrease in the Ca2+ sensitivity of rMLC phosphorylation and force production. The activity of MLCP is inhibited by Rho-associated kinase, one of the effectors of the monomeric GTPase Rho, and protein kinase C, leading to an increase in Ca2+sensitivity. Hence, smooth muscle tone appears to be regulated by a network of activating and inactivating intracellular signaling cascades.

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