EIF4E AND 4E-BP MODULATE CALCIUMHANDLING IN DROSOPHILA HEART VIA DIRECT INTERACTION BETWEEN EIF4E-4 AND SERCA PUMP

SANTALLA MANUELA; HERNANDEZ GRECO; MATTIAZZI ALICIA; GARCÍA ALEJANDRA; FERRERO PAOLA

Buenos Aires

Congreso; Reunión conjunta de sociedades biomédicas; 2017

SAFIS

We have studied the effect of genetic up and downregulation of eIF4E and 4E-BP on cardiac calcium handling using Drosophila melanogaster as genetic model. We assessed the intracellular calcium level by registering the fluorescent signal of a cardiac reporter system (TinC-Gal4; UAS-GCaMP3) in semi-intact preparation of 7days-old flies. Overexpression of 4EBP incremented the Ca2+-transient amplitude and relaxation, and the sarcoplasmic reticulum (SR) calcium load. These effects were linked to a higher SR Ca2+ reuptakethrough the Ca+2-ATPase pump (SERCA) and consequently release of Ca2+ by ryanodine receptors (RyR) was higher than control. Through bioinformatic analysis we found that SERCA possesses within its amino acid sequence the domain of interaction with eIF4E present in 4EBP (YXXXXLφ). This suggest that the results observed by the functional experiments could be due to an interaction between the eIF4E and SERCA proteins, affected probably by 4E-BP, whose eIF4E binding site is the same as that of SERCA.Using a two hybrid assay we assessed the interaction of Drosophila?s seven eIF4E isoforms with SERCA. We found that only eIF4E-4 interacts directly with SERCA. These results suggest that the effects in the activity of SERCA observed in the transgenic lines could be due to the direct interaction proved between SERCA and eIF4E-4.Our results provide evidence of the effects of modulating 4EBP in the heart of Drosophila and that these effects might be due to an interplay between 4EBP, eIF4E, more precisely its isoform 4 and SERCA.Keywords: Drosophila, heart, calcium, eIF4E, 4EBP, SERCA