Enlargement of lysosomes and late endosomes by the overexpression of the P5-ATPase ATP13A2

CORRADI GERARDO RAUL; DE LA HERA DIEGO P; ADAMO HUGO PEDRO; DE TEZANOS PINTO FELICITAS

San Javier, Tucuman

Encuentro; XLI Reunion Anual de la Sociedad Argentina de Biofisica; 2012

Sociedad Argentina de Biofisica

The P-type ion pumps are membrane transporters energized by ATP-hydrolysis. They are classified into five subfamilies termed P1-P5. P5-ATPases are ubiquitously expressed only in eukaryotes. The ion transported by these enzymes is still unknown. Five genes named ATP13A1-ATP13A5 that belong to this group of P5-ATPases have been identified in humans. Mutations of the human gene ATP13A2 underlie a juvenile form of Parkinson disease (PD) while the interruption of gene ATP13A4 was detected in patients with autism spectrum disorder (ASD) and specific language impairment (SLI).We have recently shown that overexpression of ATP13A2 pump in CHO cells (CHO-ATP13A2) increases the uptake of spermidine. The mechanism of cellular incorporation of spermidine is not known but it has been suggested that this polyamine is rapidly sequestered in lysosomes and late endosomes by means of an outward proton gradient. Consistently with this idea we have previously shown that the fluorescence intensity of the acidotropic agent acridine orange is increased in CHO-ATP13A2 cells. Here we show that the cytotoxic effect of the vacuolar H+ pump inhibitor chloroquine was similar in CHO-ATP13A2 and control cells. This result suggest that overexpression of ATP13A2 cannot substitute for the vacuolar H+ pump function. In addition, CHO-ATP13A2 cells labeled with monodansylcadaverine, a specific marker of lysosomes and late endosomes, showed an enlargement of these vesicles. Moreover, we found that CHO-ATP13A2 cells were 40-45% more resistant to FeCl3 than control cells. Because the storage of Fe3+ in a non active-redox state is favored by autophagy, these results suggest that overexpression of ATP13A2 stimulates the autophagic flux. This is consistent with a recent study showing that ATP13A2 silencing reduces macroautophagy.