Knockout of DAPIT protein disrupts ATP synthase oligomerisation and has a profound role in regulation of glucose homeostasis
Drasnarova Z1, Pecina P1, Nuskova H1, Kovalcikova J1, Zidek V1, Landa V1, Kaplanova V1, Kolar F1, Papousek F1, Sedmera D1, Kazdova L2, Bardova K1, Tauchmannova K1, Drahota Z1, Kopecky J1, Pravenec M1, Houstek J1, Mracek T1
1Institute of Physiology, Czech Academy of Sciences; 2Institute of Clinical and Experimental Medicine, Prague, Czech Republic
FoF1-ATP synthase is the key enzyme of mitochondrial energy provision, responsible for production of most of the cellular ATP. Recently, small proteolipid DAPIT originally recognised as “diabetes associated protein in insulin sensitive tissues” (also termed Usmg5) of 7 kDa has been found to be loosely attached to the enzyme, but its biological role is largely enigmatic. To elucidate the importance of this novel protein we produced ZFN rat knockout model of DAPIT deficiency on unique SHR background.
DAPIT -/- animals were fully viable and contrary to previous data on cell lines, we observed normal levels of fully assembled ATP synthase, however, it was predominantly present in the monomeric form. Both ADP phosphorylating and hydrolysing activities were reduced by circa 10% in both liver and heart.
DAPIT -/- animals had 20-30% lower body weight and pronounced decrease in total adiposity (by 40%). Based on indirect calorimetry, DAPIT -/- animals preferred glucose utilisation over other substrates, which was also replicated at the tissue level, with higher glucose oxidation in DAPIT -/- skeletal muscle. However, this is not due to the increase in glycolysis, as plasma levels of lactate did not change. Serum levels of glucose were unchanged in both fed and fasted state, but DAPIT -/- animals were significantly more insulin sensitive with decreased levels of serum insulin as well as AUC in OGTT test. Concomitantly, DAPIT -/- animals displayed decreased glucose stimulated insulin secretion from pancreatic islets.
In conclusion, absence of DAPIT protein leads towards preferential oxidation of glucose, increases insulin sensitivity and decreases total adiposity in rat. In addition, it implicates for the first time that mitochondrial ATP synthase can be directly involved in regulation of glucose homeostasis.
Supported by Czech Science Foundation grant 16-01813S.