Rab8a is involved in membrane trafficking of Kir6.2 in the MIN6 insulinoma cell line
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Although ATP-sensitive K+ (KATP) channels play an important role in the secretion of insulin by pancreatic beta cells, the mechanisms that regulate the intracellular transport of KATP channel subunit proteins (i.e., Kir6.2 and sulfonylurea receptor 1 (SUR1)) to the plasma membrane remain uncharacterized. We investigated the possibility that an interaction between KATP channel subunit proteins and Rab8a protein, a member of the RAS superfamily, may be involved in the membrane trafficking of KATP channels. Co-immunoprecipitation and immunostaining experiments using co-expression systems with fluorescent protein-tagged Kir6.2 were carried out to identify the coupling of KATP channels and Rab8a proteins in the insulin-secreting cell line, MIN6. Rab8a protein co-localized with Kir6.2 protein, a channel pore subunit (in a granular pattern), and with insulin. Knockdown of the Rab8a gene with RNA interference using small interfering RNA systems caused reductions in the amount of total KATP and plasma membrane surface KATP channels without decreasing the messenger RNA transcription of the KATP channel subunits. Rab8a gene knockdown also enhanced glucose-induced insulin secretion. These results suggest that Rab8a may be involved in membrane trafficking of KATP channels and the maintenance of normal insulin secretion in the MIN6 pancreatic beta cell line.
KeywordsChannel trafficking Insulin Kir6.2 Pancreatic beta cell MIN6 Rab8a
Aequorea coerulescens green fluorescent protein 1
Bovine serum albumin
Dulbecco’s modified Eagle’s medium
Fetal bovine serum
Glyceraldehyde 3-phosphate dehydrogenase
Guanine nucleotide exchange factor
- KATP channels
ATP-sensitive K+ channels
Inwardly rectifying K+ channel 6 family
Polymerase chain reaction
Roswell Park Memorial Institute
Sodium dodecyl sulfate
Standard error of the mean
Small interfering RNA
0.2% Tween 20 in Tris-buffered saline
We thank our colleagues for their valuable suggestions and discussion.
This work was supported in part by the Japanese Society for the Promotion of Science (JSPS) KAKENHI (M Nomura, grant number 17K09885; N Teramoto, grant number 17H02111) and Grants-in-Aid for Research Fellowship for Young Science Foundation (T Yamamoto, grant number 18K15030).
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflicts of interest.
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