Issues
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ON THE COVER
Negatively stained turkey gizzard myosin in folded (10S) conformation. See page 1081. - PDF Icon PDF LinkTable of Contents
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Editorials
Paul F. Cranefield Award to Anne E. Carlson
Trudeau recognizes the latest recipient of the Cranefield Award.
Research News
How myosin II achieves total shutdown
JGP study describes 3-D structure of the 10S form of myosin II, identifying key interactions between the head and tail domains that keep the motor protein switched off.
Commentary
Cyclic AMP links glucose stimulation to somatostatin secretion in δ-cells
Tengholm reflects on new work providing insight into the mechanisms of glucose-stimulated somatostatin secretion from δ-cells.
Comparing pathways for long-term heart rate modulation by the funny current
Heart rate control by the funny current (If) involves both fast, cAMP-dependent, and slow, membrane expression–based mechanisms to adapt to different needs.
Research Articles
Cardiac contractile dysfunction and protein kinase C–mediated myofilament phosphorylation in disease and aging
Cardiac troponin I Ser44 is a downstream target for protein kinase C. The current studies show heightened phosphorylation develops during contractile dysfunction in failing human myocardium and in rat models of pressure overload and aging with contractile dysfunction.
The central role of the tail in switching off 10S myosin II activity
Three-dimensional electron microscopy reveals that myosin II molecules are kept inactive by intramolecular interactions between the heads and the tail that inhibit actin binding, ATPase activity, filament formation, and phosphorylation. This suggests how myosin can be stored in cells with minimal energy consumption.
Glucose stimulates somatostatin secretion in pancreatic δ-cells by cAMP-dependent intracellular Ca2+ release
The regulation of somatostatin secretion from islet δ-cells remains obscure. Denwood et al. show that glucose stimulates somatostatin secretion through effects on both δ-cell electrical activity and cAMP-dependent intracellular Ca2+ release.
A stochastic model of ion channel cluster formation in the plasma membrane
Ion channels are often found in dense clusters within the plasma membranes of excitable cells. Based on experimental measurements of a wide range of channels in various cell types, Sato et al. propose that channel clusters form stochastically and that their size is regulated by a common feedback mechanism.
Communications
Triple arginines as molecular determinants for pentameric assembly of the intracellular domain of 5-HT3A receptors
Serotonin type 3A receptors are homopentameric ligand-gated ion channels that are thought to assemble via interactions involving the subunits’ extracellular and transmembrane domains. Pandhare et al. reveal that channel assembly is also determined by three arginine residues in the receptor’s intracellular domain.
Methods and Approaches
A four-electrode method to study dynamics of ion activity and transport in skeletal muscle fibers
Many cellular processes depend on the movement of ions across membranes, but current electrophysiological methods can only measure movements that generate an electrical current. Heiny et al. describe a new method to measure dynamic changes of intracellular ion concentration resulting from either electroneutral or electrogenic ion fluxes under voltage or current clamp.
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