Tyramine induces dynamic RNP granule remodeling and translation activation in the Drosophila brain

Abstract

Ribonucleoprotein (RNP) granules are dynamic condensates enriched in regulatory RNA binding proteins (RBPs) and RNAs under tight spatiotemporal control. Extensive recent work has investigated the molecular principles underlying RNP granule assembly, unraveling that they form through the self-association of RNP components into dynamic networks of interactions. How endogenous RNP granules respond to external stimuli to regulate RNA fate is still largely unknown. Here, we demonstrate through high-resolution imaging of intact Drosophila brains that Tyramine induces a reversible remodeling of somatic RNP granules characterized by the decondensation of granule-enriched RBPs (e.g. Imp/ZBP1/IGF2BP) and helicases (e.g. Me31B/DDX-6/Rck). Furthermore, our functional analysis reveals that Tyramine signals both through its receptor TyrR and through the calcium-activated kinase CamkII to trigger RNP component decondensation. Finally, we uncover that RNP granule remodeling is accompanied by the rapid and specific translational activation of associated mRNAs. Thus, this work sheds new light on the mechanisms controlling cue-induced rearrangement of physiological RNP condensates.

Boosting the toolbox for live imaging of translation

“…The transgenic construct was inserted into the VK00033 (BL9750) and VK00027 (BL9744) landing site using PhiC31 targeted insertion 60 . UASp-scFv-FP lines were done by inserting fragment of the scFv-FP plasmid digested with XhoI/HpaI in the UASp-scFv-sfGFP vector 6 digested with XhoI/HpaI. The transgenic construct was inserted in the VK00033 (BL9750) landing site using PhiC31 targeted insertion 60 .…”

Live and fixed imaging of translation sites at single mRNA resolution in the Drosophila embryo

“… Note: Fly lines maternally expressing scFv-sfGFP and scFv-mScarlet ( Dufourt et al., 2021 ) are also available. There are also UASp-scFv-sfGFP ( Lu et al, 2016 ) and UASp-scFv-GFP-NLS ( Formicola et al., 2021 ) stocks that are compatible with the GAL4/UAS system, allowing translation to be imaged in a cell type specific manner at later developmental stages ( Formicola et al., 2021 ). Transfer at least 100 females and 50 males to a collection cage with an apple juice agar plate and yeast paste.…”

Repressor sequestration activates translation of germ granule localized mRNA

“…For live imaging of suntag-nanos mRNA translation, we expressed UAS-suntag-nos (WT or SREmut) with a weak Matα-GAL4 (without VP16) maternal driver line to prevent scFv-GFP depletion which can cause artifact (Extended Data Fig. 2) 14,15 . Unfertilized embryos were collected from Vasa-mApple/Matα-GAL4; uas-suntag-nos (WT or SREmut)/scFv-GFP virgin female flies that mated with sterile male flies (male progeny of osk301/oskCE4 flies).…”

“…disassembly 7,8,[14][15][16] . Conversely, it has been elusive but curious whether RNP granules can also activate the translation of stored mRNA 9 .…”