J. Biol. Chem., Vol. 262, Issue 21, 9952-9955, Jul, 1987
Metabolism of inositol 1,3,4-trisphosphate to a new tetrakisphosphate isomer in angiotensin-stimulated adrenal glomerulosa cells
T Balla, G Guillemette, AJ Baukal and KJ Catt
Angiotensin stimulates rapid and prominent increases in inositol
polyphosphates and their metabolites in bovine glomerulosa cells labeled
with [3H]inositol. In addition to the early formation of inositol
1,4,5-trisphosphate (Ins-1,4,5-P3) and inositol 1,3,4- trisphosphate
(Ins-1,3,4-P3), as well as their intermediate product, inositol
1,3,4,5-tetrakisphosphate (Ins-1,3,4,5-P4), delayed increases in two new
InsP4 isomers were consistently observed by high resolution high
performance liquid chromatography. Studies on the metabolism of purified
Ins-1,3,4,5-P4 preparations, labeled with [3H]inositol and 32P to monitor
sites of dephosphorylation, were performed in permeabilized glomerulosa
cells. In addition to rapid degradation of Ins-1,3,4,5-P3 to Ins-1,3,4-P3
and then to Ins-3,4-P2, there was delayed formation of one of the putative
InsP4 isomers observed during AII stimulation in intact cells. The kinetics
of formation of the new InsP4 isomer, and the lack of phosphate in its 5
position based on isotope ratios, were consistent with its origin from
Ins-1,3,4-P3. This was confirmed by the conversion of [3H]Ins-1,3,4-P3 to
the new InsP4 isomer in permeabilized cells by a kinase distinct from that
which phosphorylates Ins-1,4,5-P3. These results have demonstrated that the
dephosphorylation sequence of Ins-1,4,5-P3 metabolism is accompanied by a
complex cycle of higher phosphorylations with formation of new
intermediates of potential significance in cellular regulation.