L. Missiaen et al., PARTIAL CALCIUM-RELEASE IN RESPONSE TO SUBMAXIMAL INOSITOL 1,4,5-TRISPHOSPHATE RECEPTOR ACTIVATION, Molecular and cellular endocrinology, 98(2), 1994, pp. 147-156
Even a prolonged application of a submaximal dose of Ins(1,4,5)P-3 is
unable to release the same amount of Ca2+ from the Ins(1,4,5)P-3-sensi
tive store as a higher dose of Ins(1,4,5)P-3. Low doses of Ins(1,4,5)P
-3 therefore only induce a partial release of the stored Ca2+. In this
review, we will focus on the mechanisms that may contribute to this b
ehaviour. Molecular heterogeneity of the Ins(1,4,5)P-3 receptor can co
ntribute to such behaviour if ail the gene products and alternatively
spliced isoforms would have different functional properties and be loc
ated in different store units. We will show that the control of the In
s(1,4,5)P-3 receptor by luminal Ca2+ also contributes to the partial r
elease behaviour; it can set the sensitivity of the Ins(1,4,5)P-3 rece
ptor and the decreasing luminal Ca2+ concentration may inhibit further
release while some Ca2+ is still left in the store. It is finally pos
sible that the Ins(1,4,5)P-3 receptor may adapt to a maintained stimul
us.