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Ashay D Bhatwadekar, Yucheng Xiao, Theodore Cummins, Qianyi Luo; Clock Gene Bmal1 Mediates Insulin Receptor Signaling and Kir4.1 Channels in Retinal Müller Cells. Invest. Ophthalmol. Vis. Sci. 2018;59(9):3555.
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© ARVO (1962-2015); The Authors (2016-present)
Müller cells regulate potassium balance in the retina via inwardly rectifying Kir4.1 channels. We previously reported that diurnal rhythm of Kir4.1 channels is altered during diabetes and clock gene Bmal plays an important role in regulating Kir4.1 expression. Insulin receptor substrate 1 (IRS-1) is an important regulator of insulin signaling and our studies suggest that signaling mediated via IRS-1 is necessary for Kir4.1 expression. For this study, we hypothesize that the signaling mediated by IRS-1 promotes nuclear entry of BMAL1 leading to activation of Kir4.1 channels.
The db/db and db/m mice were maintained under regular light and dark conditions. The Müller cells were isolated to determine the Kir4.1 currents. The retinal Bmal1 and IRS1 expression were determined using western blot. The rat Müller (rMC-1) cells were transfected with siRNA for IRS1. The cell lysates were separated in cytoplasmic and nuclear fractions followed by staining with BMAL1 antibodies.
The Bmal1 and IRS1 exhibited a diurnal rhythm in the retina, with diabetes there was a decrease in Bmal and IRS1 levels with an altered rhythm of these proteins. The Müller cells isolated from db/db mice demonstrated a significant decrease (p<0.01) in Kir4.1 currents when compared to db/m mice. The silencing of IRS1 reduced nuclear levels of BMAL1 with a concurrent increase in cytoplasmic BMAL1; the Kir4.1 expression was decreased subsequently in IRS silenced rMC-1 cells.
Our studies demonstrate that clock gene Bmal1 is an important downstream mediator of IRS1 signaling and its nuclear entry may play an important role in regulating Kir4.1 channels. In conclusion, our studies unravel the critical role of clock regulatory mechanisms in Müller cell dysfunction in diabetes.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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