Functional properties of the Drosophila melanogaster inositol 1, 4, 5-trisphosphate receptor mutants

Srikanth, Sonal ; Wang, Zhengnan ; Tu, Huiping ; Nair, Shalima ; Mathew, M. K. ; Hasan, Gaiti ; Bezprozvanny, Ilya (2004) Functional properties of the Drosophila melanogaster inositol 1, 4, 5-trisphosphate receptor mutants Biophysical Journal, 86 (6). pp. 3634-3646. ISSN 0006-3495

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The inositol (1,4,5)-trisphosphate receptor (InsP3R) is an intracellular calcium (Ca2+) release channel that plays a crucial role in cell signaling. In Drosophila melanogaster a single InsP3R gene (itpr) encodes a protein (DmInsP3R) that is ~60% conserved with mammalian InsP3Rs. A number of itpr mutant alleles have been identified in genetic screens and studied for their effect on development and physiology. However, the functional properties of wild-type or mutant DmInsP3Rs have never been described. Here we use the planar lipid bilayer reconstitution technique to describe single-channel properties of embryonic and adult head DmInsP3R splice variants. The three mutants chosen in this study reside in each of the three structural domains of the DmInsP3R-the amino-terminal ligand binding domain (ug3), the middle-coupling domain (wc703), and the channel-forming region (ka901). We discovered that 1), the major functional properties of DmInsP3R (conductance, gating, and sensitivity to InsP3 and Ca2+) are remarkably conserved with the mammalian InsP3R1; 2), single-channel conductance of the adult head DmInsP3R isoform is 89 pS and the embryonic DmInsP3R isoform is 70 pS; 3), ug3 mutation affects sensitivity of the DmInsP3Rs to activation by InsP3, but not their InsP3-binding properties; 4), wc703 channels have increased sensitivity to modulation by Ca2+; and 5), homomeric ka901 channels are not functional. We correlated the results obtained in planar lipid bilayer experiments with measurements of InsP3-induced Ca2+ fluxes in microsomes isolated from wild-type and heterozygous itpr mutants. Our study validates the use of D. melanogaster as an appropriate model for InsP3R structure-function studies and provides novel insights into the fundamental mechanisms of the InsP3R function.

Item Type:Article
Source:Copyright of this article belongs to Biophysical Society.
ID Code:14842
Deposited On:12 Nov 2010 13:30
Last Modified:16 May 2016 23:48

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