The central regulator of adipogenesis, PPARc, is a nuclear receptor that is linked to obesity and metabolic diseases. Here we report that MKRN1 is an E3 ligase of PPARc that induces its ubiquitination, followed by proteasome-dependent degradation. Furthermore, we identified two lysine sites at 184 and 185 that appear to be targeted for ubiquitination by MKRN1. Stable overexpression of MKRN1 reduced PPARc protein levels and suppressed adipocyte differentiation in 3T3-L1 and C3H10T1/2 cells. In contrast, MKRN1 depletion stimulated adipocyte differentiation in these cells. Finally, MKRN1 knockout MEFs showed an increased capacity for adipocyte differentiation compared with wild-type MEFs, with a concomitant increase of PPARc and adipogenic markers. Together, these data indicate that MKRN1 is an elusive PPARc E3 ligase that targets PPARc for proteasomal degradation by ubiquitin-dependent pathways, and further depict MKRN1 as a novel target for diseases involving PPARc. Cell Death and Differentiation (2014) 21, 594-603; doi:10.1038/cdd.2013.181; published online 13 December 2013Excessive body fat in obese individuals is considered a major cause of insulin resistance, cardiovascular diseases, and diabetes.1 In obesity, adipocytes alter the status of energy homeostasis by the generation of adipokines, demonstrating that adipocytes have active roles in energy homeostasis and body composition, in addition to storage of triglycerides.

SD-OCT PPAA detects localized RNFLDs with high sensitivity and specificity, which are comparable to the cpRNFL thickness profile of OCT. These findings suggest that the PPAA can be complementary to other tests for diagnosing glaucoma in patients with localized RNFLDs.

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