Distinct roles of arrestin 1 protein in photoreceptors during Drosophila development.
Arrestin regulates many facets of G-protein coupled receptor signaling. In Drosophila, Arrestin 1 (Arr1) is expressed at a lower level than Arrestin 2 (Arr2), and the role of Arr1 in visual physiology is less understood. Here we generated transgenic flies expressing enhanced green fluorescent protein tagged Arr1 (Arr1-eGFP) and explored its trafficking in live photoreceptors. We show that Arr1-eGFP is localized in the cytoplasm and displays light-dependent translocation to the rhabdomere possibly by interacting with photoactivated rhodopsin 1 (Rh1*). In the adult, translocation of Arr1-eGFP occurs with slower kinetics when compared with that of Arr2-eGFP. This slower kinetic activity may be attributable to a reduced level of phosphorylated Rh1*. Indeed, a reduced level of phosphorylated Rh1* recruits a lower level of Arr1-eGFP to rhabdomeres. To investigate whether Arr1 is required for the deactivation of phosphorylated Rh1*, we show that in flies with reduced Arr1 prolonged depolarizing afterpotential can be triggered with fewer light pulses, indicating that inactivation of phosphorylated Rh1* is compromised when the Arr1 level is reduced. Consistently, Arr1 is no longer required for deactivation of Rh1 in flies expressing phosphorylation-deficient Rh1. Previously it was reported that Arr1 displays light-dependent internalization. Unexpectedly, in adult photoreceptors we failed to observe endocytosis of Arr1-eGFP. In contrast, we show that in pupal photoreceptors Arr1-eGFP becomes internalized and sequestered in vesicles within the cytoplasm. Taken together, we propose that Arr1 plays distinct roles during development and adulthood. Arr1 orchestrates the recycling of phosphorylated Rh1* in pupae whereas it regulates the deactivation in adult.
From the Department of Pharmacology and the Center for Molecular Neuroscience and the Vision Research Center, Vanderbilt University, Nashville, Tennessee 37232 bih-hwa.shieh@vanderbilt.edu.
Bih-Hwa
BH
Shieh
From the Department of Pharmacology and the Center for Molecular Neuroscience and the Vision Research Center, Vanderbilt University, Nashville, Tennessee 37232.
Inga
I
Kristaponyte
From the Department of Pharmacology and the Center for Molecular Neuroscience and the Vision Research Center, Vanderbilt University, Nashville, Tennessee 37232.
Yuan
Y
Hong
D000818:Animals; D019390:Arrestins / Q000235:genetics / Q000378:metabolism*; D004330:Drosophila / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D010786:Photoreceptor Cells / Q000378:metabolism*; D021381:Protein Transport; D011679:Pupa / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D012243:Rhodopsin / Q000235:genetics / Q000378:metabolism
C504665:Arr1 protein, Drosophila; D019390:Arrestins; D029721:Drosophila Proteins; D012243:Rhodopsin
Arrestin; Protein Translocation; Receptor Endocytosis; Rhodopsin; Trafficking; Visual Transduction