title: Interaction with GM130 during HERG ion channel trafficking. Disruption by type 2 congenital long QT syndrome mutations. Human Ether-à-go-go-Related Gene.
abstract: Many mutations in the Human Ether-à-go-go-Related Gene (HERG) cause type 2 congenital long QT syndrome (LQT2) by disrupting trafficking of the HERG-encoded potassium channel. Beyond observations that some mutations trap channels in the endoplasmic reticulum, little is known about how trafficking fails. Even less is known about what checkpoints are encountered in normal trafficking. To identify protein partners encountered as HERG channels are transported among subcellular compartments, we screened a human heart library with the C terminus of HERG using yeast two-hybrid technology. Among the proteins isolated was GM130, a Golgi-associated protein involved in vesicular transport. The interaction mapped to two non-contiguous regions of HERG and to a region just upstream of the GRASP-65 interaction domain of GM130. GM130 did not interact with the N or C terminus of either KvLQT1 or Shaker channels. LQT2-causing mutations in the HERG C terminus selectively disrupted interactions with GM130 but not Tara, another HERG-interacting protein. Native GM130 and stably expressed HERG were co-immunoprecipitated from HEK-293 cells using GM130 antibodies. In rat cardiac myocytes and HEK-293 cells, confocal immunocytochemistry showed co-localization of GM130 and HERG to the Golgi apparatus. Overexpression of GM130 suppressed HERG current amplitude in Xenopus oocytes, as if by providing an excess of substrate at the Golgi checkpoint. These findings indicate that GM130 plays a previously undefined role in cargo transport. We propose that the cytoplasmic C terminus of HERG participates in the tethering or possibly targeting of HERG-containing vesicles within the Golgi via its interaction with GM130.
authors.affiliation: Department of Physiology, University of Wisconsin, Madison, Wisconsin 53706, USA.
authors.forename: Elon C Roti
authors.initials: EC
authors.lastname: Roti
authors.forename: Cena D
authors.initials: CD
authors.lastname: Myers
authors.forename: Rebecca A
authors.initials: RA
authors.lastname: Ayers
authors.forename: Dorothy E
authors.initials: DE
authors.lastname: Boatman
authors.forename: Samantha A
authors.initials: SA
authors.lastname: Delfosse
authors.forename: Edward K L
authors.initials: EK
authors.lastname: Chan
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Ackerman
authors.forename: Craig T
authors.initials: CT
authors.lastname: January
authors.forename: Gail A
authors.initials: GA
authors.lastname: Robertson
mesh_terms: D000818:Animals; D001324:Autoantigens; D015153:Blotting, Western; D027682:Cation Transport Proteins; D002460:Cell Line; D002478:Cells, Cultured; D018076:DNA, Complementary / Q000378:metabolism; D004268:DNA-Binding Proteins; D000072237:ERG1 Potassium Channel; D004594:Electrophysiology; D051638:Ether-A-Go-Go Potassium Channels; D015723:Gene Library; D006056:Golgi Apparatus / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D008133:Long QT Syndrome / Q000235:genetics*; D008565:Membrane Proteins / Q000378:metabolism*; D008957:Models, Genetic; D009154:Mutation; D009206:Myocardium / Q000378:metabolism; D009865:Oocytes / Q000378:metabolism; D015221:Potassium Channels / Q000235:genetics* / Q000378:metabolism; D024642:Potassium Channels, Voltage-Gated; D011233:Precipitin Tests; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D051381:Rats; D015534:Trans-Activators; D000071230:Transcriptional Regulator ERG; D020798:Two-Hybrid System Techniques; D014981:Xenopus
chemical_list: D001324:Autoantigens; D027682:Cation Transport Proteins; D018076:DNA, Complementary; D004268:DNA-Binding Proteins; C072312:ERG protein, human; D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels; C097741:Golgin subfamily A member 2; C000606913:KCNH2 protein, human; C092509:KCNH6 protein, human; D008565:Membrane Proteins; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D015534:Trans-Activators; D000071230:Transcriptional Regulator ERG