Role of mitochondrial phosphate carrier in metabolism-secretion coupling in rat insulinoma cell line INS-1.
In pancreatic β-cells, glucose-induced mitochondrial ATP production plays an important role in insulin secretion. The mitochondrial phosphate carrier PiC is a member of the SLC25 (solute carrier family 25) family and transports Pi from the cytosol into the mitochondrial matrix. Since intramitochondrial Pi is an essential substrate for mitochondrial ATP production by complex V (ATP synthase) and affects the activity of the respiratory chain, Pi transport via PiC may be a rate-limiting step for ATP production. We evaluated the role of PiC in metabolism-secretion coupling in pancreatic β-cells using INS-1 cells manipulated to reduce PiC expression by siRNA (small interfering RNA). Consequent reduction of the PiC protein level decreased glucose (10 mM)-stimulated insulin secretion, the ATP:ADP ratio in the presence of 10 mM glucose and elevation of intracellular calcium concentration in response to 10 mM glucose without affecting the mitochondrial membrane potential (Δψm) in INS-1 cells. In experiments using the mitochondrial fraction of INS-1 cells in the presence of 1 mM succinate, PiC down-regulation decreased ATP production at various Pi concentrations ranging from 0.001 to 10 mM, but did not affect Δψm at 3 mM Pi. In conclusion, the Pi supply to mitochondria via PiC plays a critical role in ATP production and metabolism-secretion coupling in INS-1 cells.
Department of Diabetes and Clinical Nutrition, Graduate School of Medicine, Kyoto University, 54 Shogoin Kawahara-cho, Sakyo-ku, Kyoto 606-8507, Japan.
Yuichi
Y
Nishi
Shimpei
S
Fujimoto
Mayumi
M
Sasaki
Eri
E
Mukai
Hiroki
H
Sato
Yuichi
Y
Sato
Yumiko
Y
Tahara
Yasuhiko
Y
Nakamura
Nobuya
N
Inagaki
D000818:Animals; D019556:COS Cells; D045744:Cell Line, Tumor; D002522:Chlorocebus aethiops; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D005947:Glucose / Q000494:pharmacology; D007328:Insulin / Q000378:metabolism; D000078790:Insulin Secretion; D007340:Insulinoma / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D008660:Metabolism / Q000187:drug effects / Q000235:genetics* / Q000502:physiology; D024101:Mitochondrial Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D010190:Pancreatic Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D028061:Phosphate Transport Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D010710:Phosphates / Q000494:pharmacology; D028081:Proton-Phosphate Symporters / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D034741:RNA, Small Interfering / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D055571:Secretory Pathway / Q000187:drug effects / Q000235:genetics* / Q000502:physiology
D007328:Insulin; D024101:Mitochondrial Proteins; D028061:Phosphate Transport Proteins; D010710:Phosphates; D028081:Proton-Phosphate Symporters; D034741:RNA, Small Interfering; C561062:SLC25A3 protein, rat; D005947:Glucose