Localization of Ubiquitin C-Terminal Hydrolase L1 in Mouse Ova and Its Function in the Plasma Membrane to Block Polyspermy

Abstract

Protein degradation is essential for oogenesis and embryogenesis. The ubiquitin-proteasome system regulates many cellular processes via the rapid degradation of specific proteins. Ubiquitin carboxylterminal hydrolase L1 (UCH-L1) is exclusively expressed in neurons , testis , ovary , and placenta , each of which has unique biological activities. However , the functional role of UCH-L1 in mouse oocytes remains unknown. Here , we report the expression pattern of UCH-L1 and its isozyme UCH-L3 in mouse ovaries and embryos. Using immunocytochemistry , UCH-L1 was selectively detected on the plasma membrane , whereas UCH-L3 was mainly detected in the cytoplasm, suggesting that these isozymes have distinct functions in mouse eggs. To further investigate the functional role of UCH-L1 in mouse eggs, we analyzed the fertilization rate of UCH-L1-deficient ova of gad female mice. Female gad mice had a significantly increased rate of polyspermy in in vitro fertilization assays, although the rate of fertilization did not differ significantly from wild-type mice. In addition, the litter size of gad female mice was significantly reduced compared with wild-type mice. These results may identify UCH-L1 as a candidate for a sperm-oocyte interactive binding or fusion protein on the plasma membrane that functions during the block to polyspermy in mouse oocytes.

Maternal control of early mouse development

“…It has a subcortical location and is excluded from cell-cell contacts, as occurs with the SCMC. Decreased fecundity is observed in mice lacking UCHL1, which might be partly due to increased rates of polyspermy, the basis of which remains unknown (Table 1) (Sekiguchi et al, 2006). Whether or not these proteins directly participate in the SCMC remains to be determined.…”

Membrane-associated farnesylated UCH-L1 promotes α-synuclein neurotoxicity and is a therapeutic target for Parkinson's disease

“…UCH-L1 is associated with the plasma membrane of oocytes (2) and with rat brain synaptic vesicles (26). To probe the potential basis for these observations, we studied the membrane-binding characteristics of UCH-L1 in synaptic vesicles isolated from rat brain.…”

“…acid protein whose expression is limited to few tissues, including brain, testes (1), ovaries (2), and certain peripheral tumors (3)(4)(5). UCH-L1 is robustly expressed in neurons, comprising 1-2% of total brain protein (6), and its absence in mice due to spontaneous intragenic deletions produces neurologic and neurodegenerative phenotypes (1,7).…”

Effects of ubiquitin C-terminal hydrolase L1 deficiency on mouse ova

“…However, the role of UCHL1 in ova is largely unknown. We previously reported that UCHL1 is exclusively localized on the plasma membrane of mouse ova and plays an important role in the polyspermy block (Sekiguchi et al 2006). Polyspermic fertilization refers to the penetration of ova by two or more spermatozoa, resulting in the developmental failure of the zygote (Sun 2003).…”

“…Susor et al (2010) showed that UCHL1 regulates CG reorganization and contributes to the ZP block using UCHL1 inhibitors. In contrast, 'gracile axonal dystrophy' (gad) female mice, which are autosomal recessive, spontaneous mutants carrying an intragenic deletion of the gene encoding UCHL1, show a significantly increased in vitro polyspermy rate and a decrease in litter size, even though gad mouse ova undergo a normal zona reaction (Saigoh et al 1999, Sekiguchi et al 2006. Thus, the role of UCHL1 in the mechanism of inhibiting polyspermy in mouse ova remains unclear.…”