Siah-1 Protein Is Necessary for High Glucose-induced Glyceraldehyde-3-phosphate Dehydrogenase Nuclear Accumulation and Cell Death in Müller Cells

E Chepchumba K Yego,Susanne Mohr

doi:10.1074/jbc.m109.083907

Abstract

The translocation and accumulation of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) in the nucleus has closely been associated with cell death induction. However, the mechanism of this process has not been completely understood. The E3 ubiquitin ligase siah-1 (seven in absentia homolog 1) has recently been identified as a potential shuttle protein to transport GAPDH from the cytosol to the nucleus. Previously, we have demonstrated that elevated glucose levels induce GAPDH nuclear accumulation in retinal Müller cells. Therefore, this study investigated the role of siah-1 in high glucose-induced GAPDH nuclear translocation and subsequent cell death in retinal Müller cells. High glucose significantly increased siah-1 expression within 12 h. Under hyperglycemic conditions, siah-1 formed a complex with GAPDH and was predominantly localized in the nucleus of Müller cells. siah-1 knockdown using 50 nm siah-1 small interfering RNA significantly decreased high glucose-induced GAPDH nuclear accumulation at 24 h by 43.8 +/- 4.0%. Further, knockdown of siah-1 prevented high glucose-induced cell death of Müller cells potentially by inhibiting p53 phosphorylation consistent with previous observations, indicating that nuclear GAPDH induces cell death via p53 activation. Therefore, inhibition of GAPDH nuclear translocation and accumulation by targeting siah-1 promotes Müller cell survival under hyperglycemic conditions.

Highlights

We have recently identified that elevated glucose levels act as a stimulus for glyceraldehyde-3-phosphate dehydrogenase (GAPDH) nuclear accumulation in retinal Muller cells via high glucose-induced activation of a caspase-1/ interleukin-1␤ signaling pathway [16]
We have demonstrated that hyperglycemia-induced GAPDH nuclear accumulation occurs in retinal Muller cells in vitro and in vivo during the development of diabetic retinopathy in rodents [4]
Effect of High Glucose on siah-1 Expression in rMC-1—We have recently shown that hyperglycemia leads to cell death of retinal Muller cells via GAPDH nuclear accumulation [4, 16]

Summary

Introduction

We have recently identified that elevated glucose levels act as a stimulus for GAPDH nuclear accumulation in retinal Muller (glia) cells via high glucose-induced activation of a caspase-1/ interleukin-1␤ signaling pathway [16]. We have demonstrated that hyperglycemia-induced GAPDH nuclear accumulation occurs in retinal Muller cells in vitro and in vivo during the development of diabetic retinopathy in rodents [4]. Because Muller cells maintain the retinal environment (34 – 39), death processes within these cells can potentially compromise their function leading to disease. The purpose of this study was to determine whether high glucose regulates siah-1 in Muller cells and to examine the potential of this protein to bind and regulate GAPDH nuclear movement and cell death under hyperglycemic conditions

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Conclusion