China
Africa
Explore chapters and articles related to this topic
Signalling Pathways in The Regulation of Cellular Responses to Exercise
Published in Peter M. Tiidus, Rebecca E. K. MacPherson, Paul J. LeBlanc, Andrea R. Josse, The Routledge Handbook on Biochemistry of Exercise, 2020
Anders Gudiksen, Stine Ringholm, Henriette Pilegaard
Adrenalin signalling is initiated when adrenaline binds to the G-coupled β2-adrenergic receptor in SkM leading to increased activity of adenylate cyclase with generation of cyclic AMP (cAMP). This is followed by activation of protein kinase A (PKA) through cAMP-induced dissociation of the catalytic and regulatory PKA subunits. The activated catalytic PKA phosphorylates glycogen phosphorylase kinase, which by phosphorylation converts glycogen phosphorylase from the inactive to the active form. Moreover, PKA has been reported to inactivate glycogen synthase by direct phosphorylation of site 2, 1a and 1b (87). In addition, PKA translocates to the nucleus with concomitant phosphorylation of target proteins, including CREB. Phosphorylated and activated CREB binds to the cAMP response element in the promoter region of target genes, which has been suggested to include PGC-1α, resulting in enhanced transcriptional activity (Figure 8.2).
Glycogen storage diseases: introduction
Published in William L. Nyhan, Georg F. Hoffmann, Aida I. Al-Aqeel, Bruce A. Barshop, Atlas of Inherited Metabolic Diseases, 2020
William L. Nyhan, Georg F. Hoffmann, Aida I. Al-Aqeel, Bruce A. Barshop
The major pathway for the catabolism of glycogen is shown in Figure 61.1. The splitting of the 1,4 linkages in glycogen is catalyzed in the presence of inorganic phosphate by phosphorylase to yield glucose-1-phosphate [10]. The phosphorylase is activated by phosphorylation of serine, which is stimulated by glucagon and epinephrine [11]. Phosphorylase kinase catalyzes the phosphorylation and activation of phosphorylase [12]. Removal of phosphate from the enzyme is catalyzed by protein phosphatase and inhibits phosphorylase activity.
Receptors and Signal Transduction Pathways Involved in Autonomic Responses
Published in Kenneth J. Broadley, Autonomic Pharmacology, 2017
cAMP serves as a second messenger in many varied physiological events by activating cAMP-dependent protein kinase (PKA). This enzyme exists as a tetramer (R2C2) consisting of two regulatory subunits (R) and two catalytic subunits (C). Two molecules of cAMP bind to each regulatory subunit causing the dissociation of two activated catalytic subunits. These catalyse the phosphorylation of a wide range of proteins, and in glycogenolysis phosphorylase kinase is activated. This enzyme is also partially activated by a rise in intracellular Ca2+ which will accompany increases in cardiac muscle contractility induced by β-adrenoceptor stimulation and hence assist in energy provision. Activated phosphorylase kinase converts phosphorylase b (inactive) to phosphorylase a (active) by phosphorylation of a serine residue (Ser-14). This is the enzyme that controls the rate-limiting step in glycogenolysis, whereby glucose units are removed sequentially, as glucose-1-phosphate, from the glycogen polymer by phosphorolytic cleavage of the α-1,4 linkages. By the action of phosphoglucomutase, this in turn is converted to glucose-6-phosphate, which is utilized as a major energy source in muscles by incorporation into glycolysis pathways with the ultimate generation of ATP and pyruvate.
The Diagnostic Yield of Electromyography at Detecting Abnormalities on Muscle Biopsy: A Single Center Experience
Published in The Neurodiagnostic Journal, 2021
Patrick B. Moloney, Stela Lefter, Aisling M. Ryan, Michael Jansen, Niamh Bermingham, Brian McNamara
Binary diagnostic outcomes (normal or abnormal) for EMG and muscle biopsy are shown in Figure 1. Abnormal EMG produced sensitivity of 87% and a PPV of 89% for abnormal muscle biopsy. Seventeen “false negative” (normal EMG and abnormal muscle biopsy) cases were identified, of which 13 had myopathic findings and 4 had neurogenic findings on muscle biopsy. Six of those “false negative” cases had pathological features consistent with a specific myopathy: mitochondrial myopathy in 4 cases; central core myopathy in 1 case; and a glycogen metabolism disorder in 1 case (phosphorylase kinase deficiency confirmed by genetic testing). There were 14 “false positive” (abnormal EMG and normal muscle biopsy) studies, of which 8 had myopathic findings and 6 had neurogenic findings on EMG.
The role of CaMK4 in immune responses
Published in Modern Rheumatology, 2018
Tomohiro Koga, Atsushi Kawakami
Calcium/calmodulin-dependent protein kinases (CaMKs) are enzymes activated similarly by calcium flux. Members of the CaMK family are classified into two classes based on their function. There are multifunctional CaMKs (CaMKK, CaMK1, CaMK2 and CaMK4) which each have several substrates and substrate-specific CaMKs (CaMK3, phosphorylase kinase, and the myosin light chain kinases) that have a single substrate [9]. Among the CaMK family, CaMK2 and CaMK4 have shown to play important roles in immune responses including T-cell activation [10,11] and T-cell development [12,13]. Comparing that CaMK2 induces NF-κB related signals [14], CaMK4 activates various transcription factors [15].
The role of IL-17 in systemic lupus erythematosus and its potential as a therapeutic target
Published in Expert Review of Clinical Immunology, 2019
Tomohiro Koga, Kunihiro Ichinose, Atsushi Kawakami, George C. Tsokos
Calcium/calmodulin-dependent protein kinases (CaMKs) are enzymes activated in a similar manner by calcium flux. Members of the CaMK family are classified into two classes based on their function. Multifunctional CaMKs (CaMKK, CaMK1, CaMK2 and CaMK4) each have several substrates, and substrate-specific CaMKs (CaMK3, phosphorylase kinase, and the myosin light chain kinases) have a single substrate [94]. In the CaMK family, CaMK2 and CaMK4 play important roles in immune responses, including T cell activation [95,96] and T cell development [97,98].