The 12 kDa FK506-binding protein, FKBP12, modulates the Ca(2+)-flux properties of the type-3 ryanodine receptor.

We have characterised the functional regulation of the type-3 ryanodine receptor by the 12 kDa FK506-binding protein. Wild-type type-3 ryanodine receptor and mutant type-3 ryanodine receptor in which the critical valine at position 2322 in the central 12 kDa FK506-binding protein binding site was substituted by aspartate, were stably expressed in human embryonic kidney cells. In contrast to the wild-type receptor, the mutant receptor was strongly impaired in binding to immobilised glutathione S-transferase 12 kDa FK506-binding protein.

Microtubule-dependent redistribution of the type-1 inositol 1,4,5-trisphosphate receptor in A7r5 smooth muscle cells.

In A7r5 vascular smooth muscle cells, the two expressed inositol 1,4,5-trisphosphate receptor (IP(3)R) isoforms were differentially localized. IP(3)R1 was predominantly localized in the perinuclear region, whereas IP(3)R3 was homogeneously distributed over the cytoplasm. Prolonged stimulation (1-5 hours) of cells with 3 microM arginine-vasopressin induced a redistribution of IP(3)R1 from the perinuclear region to the entire cytoplasm, whereas the localization of IP(3)R3 appeared to be unaffected.

Ca(2+) signals in Pmr1-GFP-expressing COS-1 cells with functional endoplasmic reticulum.

We studied the role of the Pmr1-containing Ca(2+) store in COS-1 cells endowed with a functional endoplasmic reticulum. Transfected cells could be recognized by using a green-fluorescent-protein (GFP)-tagged form of Pmr1. Pmr1-GFP fluorescence showed a typical juxtanuclear Golgi-like distribution.