<b>Physiological Functions of LMP2 B1i in the Female Reproductive System</b> The ubiquitin proteasome system UPS is essential for many cellular processes, including the cell cycle, the regulation of gene expression and cell survival. Dysfunctional UPS can be associated with the underlying pathophysiology of specific diseases. The 20S proteasome core is composed of 28 subunits, which are arranged in four stacked rings, resulting in a barrel shaped structure. The two end rings are each formed by seven subunits, and the two central rings are each formed by seven subunits. The The over expression of LMP2 1i in trophoblast cells of hydatidiform moles may contribute to its highly invasive phenotype. LMP2 1i deficient mice reportedly exhibit uterine neoplasms, with a disease prevalence of 36 by 12 months of age. Embryo implantation involves the invasion of placental extravillous trophoblast cells EVTs into the uterus. Normal human placentas or placentas from hydatidiform mole patients were collected and the expression of LMP2 1i in different cell types including trophoblastic column TC , cytotrophoblast cells CTB and syncytiotrophoblasts STBs was examined under different pathological states by pathological analysis. The expression of LMP2 1i in TC of partial hydatidiform mole and complete hydatidiform mole placentas, was higher than that in TC of normal human placentas. Further the experiments with human and mouse uterine tissues clarified the physiological significance of LMP2 1i in malignant myometrium transformation. In this mini review, we covered recent insights into the molecular pathways involved in LMP2 1i mediated physiological functions, with a particular focus on embryo implantation and uterine mesenchymal tumorigenesis. LMP2 1i, implantation, trophoblast, leiomyosarcoma, leiomyoma 597-600 Issue-4 Volume-3 Takuma Hayashi | Kenji Sano | Tomoyuki Ichimura | Gal Gur | Hiroyuki Aburatani | Yae Kanai | Dorit Zharhary | Susumu Tonegawa | Nobuo Yaegashi | Ikuo Konishi