Mkrn3 functions as a novel ubiquitin E3 ligase to inhibit Nptx1 during puberty initiation

// Huifang Liu 1 , Xiangxin Kong 1 and Fengling Chen 1 1 Department of Endocrinology, Shanghai Ninth People’s Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China Correspondence to: Fengling Chen, email: chenfengling@sjtu.edu.cn Keywords: puberty, Mkrn3, Nptx1, ubiquitination, hypothalamus Received: January 18, 2017 Accepted: June 26, 2017 Published: July 18, 2017 ABSTRACT Central precocious puberty (CPP) is attributed to the disorder of some trigger factors those can activate the hypothalamic-pituitary-gonadal axis controlled by GnRH neurons. Many recent studies reveal one of those trigger factors, Makorin ring finger protein 3 (Mkrn3), whose loss-of-function mutations are implicated in CPP. Although Mkrn3 contained zinc Ring finger domain is considered as a putative E3 ubiquitin ligase, its actual function is never reported. Here, our results demonstrated that in mice hypothalamus before and when puberty initiated, Mkrn3 expressed the reversed tendency with Nptx1, which is an important secreted protein for neuron development. Furthermore, our data manifested that Mkrn3 interacted and suppressed Nptx1 activity. And the Ring finger domain of Mkrn3 contained was determined to be essential for binding with Nptx1 for its polyubiquitination during the puberty initiation. Our study shed light on the molecular insights into the function of Mkrn3 in the events of puberty initiation.