The AMPylase FIC-1 modulates TGF-ß signaling in Caenorhabditis elegans.

Post-translational protein modifications are essential for the spatio-temporal regulation of protein function. In this study, we examine how the activity of the Caenorhabditis elegans AMPylase FIC-1 modulates physiological processes in vivo. We find that over-expression (OE) of the constitutive AMPylase FIC-1(E274G) impairs C. elegans development, fertility, and stress resilience. We also show that FIC-1(E274G) OE inhibits pathogen avoidance behavior by selectively suppressing production of the Transforming Growth Factor-ß (TGF-ß) ligands DAF-7 and DBL-1 in ASI sensory neurons. Finally, we demonstrate that FIC-1 contributes to the regulation of adult body growth, cholinergic neuron function, and larval entry into dauer stage; all processes controlled by TGF-ß signaling. Together, our results suggest a role for FIC-1 in regulating TGF-ß signaling in C. elegans.

Over-expression of the constitutive AMPylase FIC-1(E274G) does not deplete cellular ATP pools in C. elegans.

Protein AMPylation has emerged as a posttranslational protein modification regulating cellular proteostasis. AMPylation is conferred by Fic AMPylases, which catalyze the covalent attachment of AMP to target proteins at the expense of ATP. Over-expression of constitutive-active Fic AMPylases is toxic. Here, we test the hypothesis that excessive Fic AMPylase activity could deplete cellular ATP pools, leading to cell death. We find that increased/decreased Fic AMPylase activity only alters cellular ATP concentrations by approximately 15%. This suggests that hyper-AMPylation-mediated cell death is likely not the consequence of cellular ATP depletion.

Characterizing the binding of dopamine D1-D2 receptors in vitro and in temporal and frontal lobe tissue total protein.

Dysfunction of the dopaminergic pathway is linked to numerous diseases of the nervous system. The D1-D2 receptor heteromer is known to play a role in certain neuropsychiatric disorders, such as depression. Here, we synthesized an eight amino acid residue peptide, EAARRAQE, derived from the third intracellular loop of the D2 receptor and show that the peptide binds to the D1 receptor with comparable efficiency as that of the full-length D2 receptor protein. Moreover, immunoprecipitation studies show the existence of a heteromeric complex formed both in vitro and in total protein derived from temporal and frontal lobe tissue from normal and depressed subjects. The efficiency of the peptide to block the D1-D2 heteromeric complex was comparable in all the samples tested.