Homoeostatic regulation of the light sensor, rhodopsin, is critical for the maintenance of light sensitivity and survival of photore- ceptors. The major fly rhodopsin, Rhl, undergoes light-induced endocytosis and degr...Homoeostatic regulation of the light sensor, rhodopsin, is critical for the maintenance of light sensitivity and survival of photore- ceptors. The major fly rhodopsin, Rhl, undergoes light-induced endocytosis and degradation, but its protein and mRNA levels remain constant during light/dark cycles. It is not clear how translation of Rhl is regulated. Here, we show that adult photorecep- tors maintain a constant, abundant quantity of ninaE mRNA, which encodes Rhl. We demonstrate that the Fmrl protein associ- ates with ninaE mRNA and represses its translation. Further, light exposure triggers a calcium-dependent dephosphorylation of Fmrl, which relieves suppression of Rhl translation. We demonstrate that Mts, the catalytic subunit of protein phosphatase 2A （PP2A）, mediates light-induced Fmrl dephosphorylation in a regulatory B subunit of PP2A （CKa）-dependent manner. Finally, we show that blocking light-induced Rhl translation results in reduced light sensitivity. Our results reveal the molecular mechanism of Rhl homoeostasis and physiological consequence of Rhl dysregulation.展开更多
文摘Homoeostatic regulation of the light sensor, rhodopsin, is critical for the maintenance of light sensitivity and survival of photore- ceptors. The major fly rhodopsin, Rhl, undergoes light-induced endocytosis and degradation, but its protein and mRNA levels remain constant during light/dark cycles. It is not clear how translation of Rhl is regulated. Here, we show that adult photorecep- tors maintain a constant, abundant quantity of ninaE mRNA, which encodes Rhl. We demonstrate that the Fmrl protein associ- ates with ninaE mRNA and represses its translation. Further, light exposure triggers a calcium-dependent dephosphorylation of Fmrl, which relieves suppression of Rhl translation. We demonstrate that Mts, the catalytic subunit of protein phosphatase 2A （PP2A）, mediates light-induced Fmrl dephosphorylation in a regulatory B subunit of PP2A （CKa）-dependent manner. Finally, we show that blocking light-induced Rhl translation results in reduced light sensitivity. Our results reveal the molecular mechanism of Rhl homoeostasis and physiological consequence of Rhl dysregulation.
