Mitochondrial phosphate transport during nutrient stimulation of INS-1E insulinoma cells.
Here, we have investigated the role of inorganic phosphate (Pi) transport in mitochondria of rat clonal β-cells. In α-toxin-permeabilized INS-1E cells, succinate and glycerol-3-phosphate increased mitochondrial ATP release which depends on exogenous ADP and Pi. In the presence of substrates, addition of Pi caused mitochondrial matrix acidification and hyperpolarisation which promoted ATP export. Dissipation of the mitochondrial pH gradient or pharmacological inhibition of Pi transport blocked the effects of Pi on electrochemical gradient and ATP export. Knock-down of the phosphate transporter PiC, however, neither prevented Pi-induced mitochondrial activation nor glucose-induced insulin secretion. Using (31)P NMR we observed reduction of Pi pools during nutrient stimulation of INS-1E cells. Interestingly, Pi loss was less pronounced in mitochondria than in the cytosol. We conclude that matrix alkalinisation is necessary to maintain a mitochondrial Pi pool, at levels sufficient to stimulate energy metabolism in insulin-secreting cells beyond its role as a substrate for ATP synthesis.
Department of Physiology and Institute of Lifestyle Medicine, Yonsei University Wonju College of Medicine, Wonju, Republic of Korea.
Xianglan
X
Quan
Ranjan
R
Das
Shanhua
S
Xu
Gary W
GW
Cline
Andreas
A
Wiederkehr
Claes B
CB
Wollheim
Kyu-Sang
KS
Park
D000255:Adenosine Triphosphate / Q000096:biosynthesis; D000818:Animals; D001149:Arsenates / Q000494:pharmacology; D045744:Cell Line, Tumor; D005994:Glycerophosphates / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007340:Insulinoma; D053078:Membrane Potential, Mitochondrial; D008928:Mitochondria / Q000378:metabolism*; D000226:Mitochondrial ADP, ATP Translocases / Q000037:antagonists & inhibitors / Q000378:metabolism; D051336:Mitochondrial Membranes / Q000502:physiology; D010710:Phosphates / Q000378:metabolism*; D051381:Rats; D013386:Succinates / Q000378:metabolism*
D001149:Arsenates; D005994:Glycerophosphates; D010710:Phosphates; D013386:Succinates; D000255:Adenosine Triphosphate; D000226:Mitochondrial ADP, ATP Translocases; C025657:arsenic acid
(31)P NMR; ANT; As(i); DIC; DL-α-glycerol-3-phosphate; DL-αGP; Inorganic phosphate; KRB; Krebs–Ringer bicarbonate; Metabolism-secretion coupling; Mitochondrial membrane potential; Mitochondrial pH gradient; N,N,N′,N′-tetramethyl-p-phenylenediamine; P(i); P(i)C; Phosphate carrier; TMPD; adenine nucleotide translocator; dicarboxylate carrier; inorganic arsenate; inorganic phosphate; mitochondrial electrical potential; mitochondrial pH gradient; phosphate carrier; ΔpH(mito); Ψ(mito)