The puromycin-sensitive aminopeptidase PAM-1 is required for meiotic exit and anteroposterior polarity in the one-cellCaenorhabditis elegansembryo

Abstract

In the nematode Caenorhabditis elegans, sperm entry into the oocyte triggers the completion of meiosis and the establishment of the embryonic anteroposterior (AP) axis. How the early embryo makes the transition from a meiotic to a mitotic zygote and coordinates cell cycle changes with axis formation remains unclear. We have discovered roles for the C. elegans puromycin-sensitive aminopeptidase PAM-1 in both cell cycle progression and AP axis formation, further implicating proteolytic regulation in these processes. pam-1 mutant embryos exhibit a delay in exit from meiosis: thus, this peptidase is required for progression to mitotic interphase. In addition, the centrosomes associated with the sperm pronucleus fail to closely associate with the posterior cortex in pam-1 mutants,and the AP axis is not specified. The meiotic exit and polarity defects are separable, as inactivation of the B-type cyclin CYB-3 in pam-1mutants rescues the meiotic exit delay but not the polarity defects. Thus PAM-1 may regulate CYB-3 during meiotic exit but presumably targets other protein(s) to regulate polarity. We also show that the pam-1 gene is expressed both maternally and paternally, providing additional evidence that sperm-donated gene products have important roles during early embryogenesis in C. elegans. The degradation of proteins through ubiquitin-mediated proteolysis has been previously shown to regulate the cell cycle and AP axis formation in the C. elegans zygote. Our analysis of PAM-1 requirements shows that a puromycin-sensitive aminopeptidase is also required for proteolytic regulation of the oocyte to embryo transition.

Bestatin Inhibits Cell Growth, Cell Division, and Spore Cell Differentiation in Dictyostelium discoideum

“…In COS cells and Swiss 3T3 fibroblasts it localizes to the nucleus and the cytoplasm (10). PSA is involved in proteolytic events that mediate processes like cell cycle progression in mitosis and meiosis, embryogenesis, neuronal differentiation, establishment of polarity, reproduction, and processing of major histocompatibility complex class I peptides in a variety of organisms (4,10,19,27,38,39,43,44). In addition, it may have roles in cell signaling and protein trafficking, independent of its enzymatic activity (40).…”

Mutation of the Membrane-Associated M1 Protease APM1 Results in Distinct Embryonic and Seedling Developmental Defects inArabidopsis

“…PSA is important in both generating and degrading MHC peptides, although this did not appear to have a bearing on viability of the PSA-deficient mice (Towne et al, 2008). In Caenorhabditis elegans, the PAM-1 PSA ortholog has been shown to be necessary for oocyte-to-embryo transition and establishment of anterior-posterior polarity and is necessary for cells to exit meiosis (Lyczak et al, 2006). APM1 metallopeptidase activity may be important for processing of proteins required for general cellular function (housekeeping), by either activating or deactivating proteins, including proteins involved in the cell cycle or in recycling cell wall components.…”

“…Puromycin-Sensitive Aminopeptidase Than Insulin-Responsive Aminopeptidase M1 peptidases function within the cell and play essential roles in embryogenesis, reproduction, cell cycle progression, and cell viability (Brooks et al, 2003;Lyczak et al, 2006). APM1, amiopeptidase N (APN/CD13), and the puromycin-sensitive aminopeptidase (PSA) are all M1 APs with both cytosolic and membrane localization (Constam et al, 1995;de Gandarias et al, 1997;Murphy et al, 2002;Braccia et al, 2003).…”

The Catalytic and Protein-Protein Interaction Domains Are Required for APM1 Function

“…Eukaryotic M1 peptidases regulate a wide range of physiological response and developmental pathways and play essential roles in embryogenesis, reproduction, cell cycle progression, and cell viability (Constam et al, 1995;Brooks et al, 2003;Sanchez-Moran et al, 2004;Lyczak et al, 2006;Matsui et al, 2006;Walling, 2006;Peer et al, 2009). Thus far, two M1 aminopeptidases in Arabidopsis (Arabidopsis thaliana) have been characterized.…”

“…PSA knockout mice have fewer viable embryos, reduced litter size, and are smaller and less fertile or infertile compared with wild-type mice (Osada et al, 2001a(Osada et al, , 2001bTowne et al, 2008). In Caenorhabditis elegans, the APM1/PSA homolog PAM-1 has been shown to be necessary for oocyte-to-embryo transition as well as the establishment of anterior-posterior polarity (Lyczak et al, 2006). The catalytic domain of APM1 also shares sequence similarity with the mammalian insulin-responsive aminopeptidase/oxytocinase (IRAP), which processes signaling peptides like tachykinin and oxytocin (Tsujimoto et al, 1992;Herbst et al, 1997;Albiston et al, 2004), leukotriene A4 hydrolase, which activates the leukotriene A4 receptor at the cell surface (Rudberg et al, 2002), and aminopeptidase N (AP-N/ CD13), which functions in cell surface uptake of cholesterol (Kramer et al, 2005).…”