Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.3.16 (calcineurin)
 17,112 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Phosphorylation by protein kinase A and dephosphorylation by protein phosphatase 1 modulate the inhibitory activity of phospholamban (PLN), the endogenous regulator of the sarco(endo)plasmic reticulum calcium Ca(2+) ATPase (SERCA). This cyclic mechanism constitutes the driving force for calcium reuptake from the cytoplasm into the myocite lumen, regulating cardiac contractility. PLN undergoes a conformational transition between a relaxed (R) and tense (T) state, an equilibrium perturbed by the addition of SERCA. Here, we show that the single phosphoryl transfer at Ser16 induces a more pronounced conformational switch to the R state in phosphorylated PLN (pPLN). The binding affinity of PLN to SERCA is not affected (K(d) values for the transmembrane domains of pPLN and PLN are approximately 60 microM), supporting the hypothesis that phosphorylation at Ser16 does not dissociate PLN from SERCA. However, the binding surface and dynamics in domain Ib (residues 22-31) change substantially upon phosphorylation. Since PLN can be singly or doubly phosphorylated at Ser16 and Thr17, we propose that these sites remotely control the conformation of domain Ib. These findings constitute a paradigm for how post-translational modifications such as phosphorylation in the cytoplasmic portion of membrane proteins control intramembrane protein-protein interactions.
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PMID:Effects of Ser16 phosphorylation on the allosteric transitions of phospholamban/Ca(2+)-ATPase complex. 1656 56

Liver glycogen is synthesized after a meal in response to an increase in blood glucose concentration in the portal vein and endocrine and neuroendocrine signals, and is degraded to glucose between meals to maintain blood glucose homeostasis. Glycogen degradation and synthesis during the diurnal cycle are mediated by changes in the activities of phosphorylase and glycogen synthase. Phosphorylase is regulated by phosphorylation of serine-14. Only the phosphorylated form of liver phosphorylase (GPa) is catalytically active. Interconversion between GPa and GPb (unphosphorylated) is dependent on the activities of phosphorylase kinase and of phosphorylase phosphatase. The latter comprises protein phosphatase-1 in conjunction with a glycogen-targeting protein (G-subunit) of the PPP1R3 family. At least two of six G-subunits (GL and PTG) expressed in liver are involved in GPa dephosphorylation. GPa to GPb interconversion is dependent on the conformational state of phosphorylase which can be relaxed (R) or tense (T) depending on the concentrations of allosteric effectors such as glucose, glucose 6-phosphate and adenine nucleotides and on the acetylation state of lysine residues. The G-subunit, GL, encoded by PPP1R3B gene is expressed at high levels in liver and can function as a phosphorylase phosphatase and a synthase phosphatase and has an allosteric binding site for GPa at the C-terminus which inhibits synthase phosphatase activity. GPa to GPb conversion is a major upstream event in the regulation of glycogen synthesis by glucose, its downstream metabolites and extracellular signals such as insulin and neurotransmitters.
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PMID:Role of glycogen phosphorylase in liver glycogen metabolism. 2651 72

Purpose To report a case of bilateral cavernous sinus thrombosis (CST) in a patient with tacrolimus-associated posttransplant thrombotic microangiopathy. Methods Case report. Results An 8-year-old boy with a medical history of orthotopic heart transplant, posttransplant lymphoproliferative disease, and recurrent infections was hospitalized for nausea, vomiting, and diarrhea. His ocular history included accommodative esotropia, hyperopia with astigmatism, Molluscum contagiosum lid lesions, and idiopathic intracranial hypertension. Shortly after presentation, he developed increased intraocular pressure, an afferent pupillary defect, a layered hyphema, and tense proptosis of the left globe requiring an emergent canthotomy and cantholysis. Over the next month, the patient's hospital course included subdural and subarachnoid hemorrhage, temporal lobe stroke, serotonin syndrome, bilateral CST, and systemic microangiopathy. After an extensive workup, a diagnosis of tacrolimus-associated thrombotic microangiopathy was made. At this point, vision was 20/20 in the right eye and light perception in the left eye. Eight months after the canthotomy and cantholysis, the patient's vision in the left eye deteriorated to no light perception and remained so after 13 months of follow-up. Conclusions An idiosyncratic drug reaction should be considered in the differential diagnosis of CST, especially in a patient on calcineurin inhibitors after solid organ transplant without sinus disease or orbital cellulitis.
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PMID:Bilateral Cavernous Sinus Thrombosis in a Patient with Tacrolimus-Associated Posttransplant Thrombotic Microangiopathy. 2773 59