Modulation of BK channel calcium affinity by differential phosphorylation in developing ovine basilar artery myocytes

• Published in: American journal of physiology. Heart and circulatory physiology 2006-08, Vol.291 (2), p.H732-H740
• Main Authors: Lin, Mike T, Hessinger, David A, Pearce, William J, Longo, Lawrence D
• Format: Article
• Language: English
• Subjects: Aging - physiology; Alkaline Phosphatase - metabolism; Animals; Basilar Artery - cytology; Basilar Artery - growth & development; Basilar Artery - metabolism; Calcium - metabolism; Cell Separation; Cyclic AMP-Dependent Protein Kinases - metabolism; Cyclic GMP-Dependent Protein Kinases - metabolism; Female; Fetus - metabolism; Indicators and Reagents; Kinetics; Large-Conductance Calcium-Activated Potassium Channels - physiology; Membrane Potentials - physiology; Myocytes, Smooth Muscle - metabolism; Patch-Clamp Techniques; Phosphorylation; Pregnancy; Sheep
• ISSN: 0363-6135; 1522-1539
• DOI: 10.1152/ajpheart.01357.2005

1 Center for Perinatal Biology and 2 Department of Physiology and Pharmacology, Loma Linda University School of Medicine, Loma Linda, California Submitted 22 December 2005 ; accepted in final form 4 March 2006 Large-conductance Ca 2+ -sensitive K + (BK) channel activity is greater in basilar artery smooth muscle cells (SMCs) of the fetus than the adult, and this increased activity is associated with a lower BK channel Ca 2+ set point (Ca 0 ). Associated PKG activity is three times greater in BK channels from fetal than adult myocytes, whereas associated PKA activity is three times greater in channels from adult than fetal myocytes. We hypothesized that the change in Ca 0 during development results from different levels of channel phosphorylation. In inside-out membrane patch preparations of basilar artery SMCs from adult and fetal sheep, we measured BK channel activity in four states of phosphorylation: native, dephosphorylated, PKA phosphorylated, and PKG phosphorylated. BK channels from adult and fetus exhibited similar voltage-activation curves, Ca 0 values, and Ca 2+ dissociation constants ( K d ) for the dephosphorylated, PKA phosphorylated, and PKG phosphorylated states. However, voltage-activation curves of native fetal BK channels shifted significantly to the left of those of the adult, with Ca 0 and K d values half those of the adult. For the two age groups at each of the phosphorylation states, Ca 0 and K d produced linear relations when plotted against voltage at half-maximal channel activation. We conclude that the Ca 0 and K d values of the BK channel can be modulated by differential channel phosphorylation. Lower Ca 0 and K d values in BK channels of fetal myocytes can be explained by a greater extent of channel phosphorylation of fetal than adult myocytes. patch clamp; inside-out patch; fetus; development Address for reprint requests and other correspondence: L. D. Longo, Center for Perinatal Biology, Loma Linda Univ. School of Medicine, Loma Linda, CA 92350 (e-mail: llongo{at}llu.edu )