The transporter-like protein inebriated mediates hyperosmotic stimuli through intracellular signaling

• Published in: Journal of experimental biology Vol. 203; no. Pt 23; pp. 3531 - 3546
• Main Authors: Chiu, C, Ross, L S, Cohen, B N, Lester, H A, Gill, S S
• Format: Journal Article
• Language: English
• Published: England 01.12.2000
• Subjects: Amino Acid Sequence; Animals; Biological Transport; Calcium - metabolism; Carrier Proteins - chemistry; Carrier Proteins - genetics; Carrier Proteins - metabolism; Carrier Proteins - physiology; Chlorides - metabolism; Cloning, Molecular; DNA, Complementary; Drosophila - metabolism; Drosophila Proteins; GABA Plasma Membrane Transport Proteins; gamma-Aminobutyric Acid - metabolism; Inositol 1,4,5-Trisphosphate - metabolism; Ion Transport; Manduca - genetics; Manduca - metabolism; Manduca sexta; Membrane Proteins - metabolism; Membrane Transport Proteins; Molecular Sequence Data; Neuropeptides - chemistry; Neuropeptides - genetics; Neuropeptides - physiology; Oocytes; Organic Anion Transporters; Osmolar Concentration; Patch-Clamp Techniques; Plasma Membrane Neurotransmitter Transport Proteins; Potassium - metabolism; Potassium Channels - metabolism; Recombinant Fusion Proteins - metabolism; Signal Transduction; Sodium - metabolism; Type C Phospholipases - metabolism; Xenopus laevis
• ISSN: 0022-0949; 1477-9145
• DOI: 10.1242/jeb.203.23.3531

We cloned the inebriated homologue MasIne from Manduca sexta and expressed it in Xenopus laevis oocytes. MasIne is homologous to neurotransmitter transporters but no transport was observed with a number of putative substrates. Oocytes expressing MasIne respond to hyperosmotic stimulation by releasing intracellular Ca(2+), as revealed by activation of the endogenous Ca(2+)-activated Cl(-) current. This Ca(2+) release requires the N-terminal 108 amino acid residues of MasIne and occurs via the inositol trisphosphate pathway. Fusion of the N terminus to the rat gamma-aminobutyric acid transporter (rGAT1) also renders rGAT1 responsive to hyperosmotic stimulation. Immunohistochemical analyses show that MasIne and Drosophila Ine have similar tissue distribution patterns, suggesting functional identity. Inebriated is expressed in tissues and cells actively involved in K(+) transport, which suggests that it may have a role in ion transport, particularly of K(+). We propose that stimulation of MasIne releases intracellular Ca(2+) in native tissues, activating Ca(2+)-dependent K(+) channels, and leading to K(+) transport.