期刊
BIOCHEMICAL JOURNAL
卷 441, 期 -, 页码 317-323出版社
PORTLAND PRESS LTD
DOI: 10.1042/BJ20111617
关键词
calcium signalling; domain assembly; nicotinic acid-adenine dinucleotide phosphate (NAADP); two-pore channel (TPC); voltage-gated ion channel
资金
- Biotechnology and Biological Sciences Research Council [BB/G013721/1]
- BBSRC [BB/G013721/1] Funding Source: UKRI
- Biotechnology and Biological Sciences Research Council [BB/G013721/1] Funding Source: researchfish
TPCs (two-pore channels) have recently been identified as targets for the Ca2+-mobilizing messenger NAADP (nicotinic acid adenine dinucleotide phosphate). TPCs have a unique structure consisting of cytosolic termini, two hydrophobic domains (I and II) each comprising six transmembrane regions and a pore, and a connecting cytosolic loop; however, little is known concerning how these channels are assembled. In the present paper, we report that both domain I and II of human TPCs are capable of independent insertion into membranes, whereas the loop linking the domains fails to insert. Pairs of transmembrane regions within domain I of TPC1 are also capable of insertion, consistent with sequential translational integration of hydrophobic regions. Insertion of the first two transmembrane regions, however, was inefficient, indicating possible interaction between transmembrane regions during translation. Both domains, and each pair of transmembrane regions within domain I, were capable of forming oligomers, highlighting marked redundancy in the molecular determinants driving oligomer formation. Each hydrophobic domain formed dimers upon cross-linking. The first four transmembrane regions of TPC1 also formed dimers, whereas transmembrane regions 5 and 6, encompassing the pore loop, formed both dimers and tetramers. TPCs thus probably assemble as dimers through differential interactions between transmembrane regions. The present study provides new molecular insight into the membrane insertion and oligomerization of TPCs.
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