The Drosophila transient receptor potential (trp) gene and its homologue, trpl, have been suggested to mediate calcium entry during the insect's phototransduction process. We isolated human cDNA, human trp-1 (Htrp-1), encoding a polypeptide .f 793 amino acids that is 37% identical (62% similar) to Drosophila trp and trpl. Northern analysis showed that the Htrp-1 transcript is approximately 5.5 kb and expressed in most human tissues, with higher amounts in ovary, testis, heart, and brain.Isolation of Htrp-I suggests that a trp-type protein is present in mammals and should provide a useful tool in studying calciumdepletion induced calcium influx processes.:~ey words': Transient receptor potential; Calcium influx , hannel; Ca 2+ signaling ~. IntroductionCalcium regulation plays an important role in many cellular 0rocesses. In non-excitable mammalian cells, activation of i~hosphoinositide-specific phospholipase C (PLC) produces ~nositol 1,4,5-trisphosphate (IP3), which in turn causes the reease of intracellular calcium from its storage pools in the endo~lasmic reticulum. This results in a transient elevation of cyosolic-free Ca 2+, which is normally followed by a Ca 2+ influx 'rom the extracellular space. By refilling the pools, Ca 2+ influx )lays an important role in prolonging the Ca 2+ signal, allowing or localized signaling, and maintaining Ca 2÷ oscillations [1].Calcium influx in non-excitable cells is thought to occur hrough plasma membrane channels which, in contrast to the voltage-dependent Ca 2+ channels in excitable cells, are operated lot by changes of membrane potentials but rather by how full he internal Ca 2+ stores are [2]. Although studies using either luorescent Ca 2+ indicators or electrophysiological techniques lave suggested that multiple types of Ca 2+ permeant channels nay be involved in different cell types to fulfill the influx funcion, the molecular structure of the channels and the mechalism that regulates the influx have remained unclear and reprerent one of the major unanswered questions of cellular Ca -,+ !lomeostasis [3][4][5].Candidates involved in voltage-independent Ca 2+ entry into [9]. A detailed analysis of the trpl sequence showed that it shares moderate homology with voltage-dependent Ca 2+ and Na ÷ channels at their putative transmembrane regions. However, in clear contrast with the voltage-dependent channels, it lacks the positively charged amino acid residues at the presumed $4 segment which are thought to act as voltage sensors that promote gating in response to changes in membrane potentials. The structural homology to Ca 2+ and Na + channels together with the absence of charged residues in trpl and trp suggested that these proteins may form voltage-independent ion channels. This was demonstrated recently by expression of the cDNAs for trp and trpl in insect Sf9 cells using the baculovirus system. It was fount that trp forms a Ca 2÷ permeable cation channel which is activated by store depletion with thapsigargin [10] whereas trpl forms a Ca -'+ permeable non-selec...

Using conserved amino acid sequences for the design of oligonucleotide primers, we isolated cDNA clones for two subunits of the V‐ATPase from the midgut and Malpighian tubules of Aedes aegypti larvae. The 3.1 kb cDNA of the A subunit of the peripheral catalytic V1 sector codes for a protein of 68.6 kDa. The protein contains conserved motifs, including an ATP/GTP binding site, found in all other A subunits. Southern analysis using the A subunit as a probe suggests the presence of only a single copy of gene in the Aedes aegypti. The 0.85 kb cDNA of the c subunit of the membrane H+ conducting V0 sector codes for a protein of kDa. This protein has four transmembrane domains and contains a conserved glutamic acid that serves as the binding site for dicyclohexylcarbodiimide. Southern analysis using the c subunit as a probe suggests the presence of more than one related gene in the genome of Aedes aegypti. Pileup analysis of various A and c subunits shows that these subunits fall into distinct clusters, including one in which all arthropod proteins are clustered. Arch. Insect Biochem. Physiol. 37:80–90, 1998. © 1998 Wiley‐Liss, Inc.