Regulatory mechanisms for glycogenolysis and K+ uptake in brain astrocytes

Abstract

Recent advances in brain energy metabolism support the notion that glycogen in astrocytes is necessary for the clearance of neuronally-released K(+) from the extracellular space. However, how the multiple metabolic pathways involved in K(+)-induced increase in glycogen turnover are regulated is only partly understood. Here we summarize the current knowledge about the mechanisms that control glycogen metabolism during enhanced K(+) uptake. We also describe the action of the ubiquitous Na(+)/K(+) ATPase for both ion transport and intracellular signaling cascades, and emphasize its importance in understanding the complex relation between glycogenolysis and K(+) uptake.

Keywords: 1,4-dideoxy-1,4-imino-d-arabinitol; 4,4′-diisothiocyanostilbene-2,2′-disulfonic acid; AE; AMP-activated protein kinase; AMPK; Astrocytes; CA; CTS; DAB; DIDS; EGFR; ERK; GBD; GP; GS; GSK3; Glycogen; Glycogen phosphorylase; IP3R; L-type voltage-dependent Ca(2+) channel; LCC; MEK; NBC; NCX; NKA; NKCC; Na(+)/ cotransporter; Na(+)/Ca(2+) exchanger; Na(+)/K(+) ATPase; Na(+)/K(+)/2Cl(−) cotransporter; Nax; PDE; PI3K; PKA; PKB/Akt; PKC; PLC; PhK; Potassium; Raf; Ras; anion exchanger; cAMP-dependent protein kinase A; carbonic anhydrase; cardiotonic steroids; epidermal growth factor receptor; extracellular Na(+) level sensitive Na(+) channel; extracellular-signal regulated kinase; glycogen binding domain; glycogen phosphorylase; glycogen synthase; glycogen synthase kinase 3; inositol trisphosphate receptor; mitogen-activated protein and extracellular-signal regulated kinase; phosphatidylinositide 3-kinase; phosphodiesterase; phospholipase C; phosphorylase kinase; protein kinase B; protein kinase C; rapidly accelerated fibrosarcoma; rat sarcoma; sAC; soluble adenylate cyclase..