Dictyostelium puromycin-sensitive aminopeptidase A is a nucleoplasmic nucleomorphin-binding protein that relocates to the cytoplasm during mitosis

Abstract

Nucleomorphin (NumA1) is a nucleolar/nucleoplasmic protein linked to cell cycle in Dictyostelium. It interacts with puromycin-sensitive aminopeptidase A (PsaA) which in other organisms is a Zn(2+)-metallopeptidase thought to be involved in cell cycle progression and is involved in several human diseases. Here, we have shown that Dictyostelium PsaA contains domains characteristic of the M1 family of Zn(2+)-metallopeptidases: a GAMEN motif and a Zn(2+)-binding domain. PsaA colocalized with NumA1 in the nucleoplasm in vegetative cells and was also present to a lesser extent in the cytoplasm. The same localization pattern was observed in cells from slugs, however, in fruiting bodies PsaA was only detected in spore nuclei. During mitosis PsaA redistributed mainly throughout the cytoplasm. It possesses a functional nuclear localization signal ((680)RKRF(683)) necessary for nuclear entry. To our knowledge, this is the first nuclear localization signal identified in a Psa from any organism. Treatment with Ca(2+) chelators or calmodulin antagonists indicated that neither Ca(2+) nor calmodulin is involved in PsaA localization. These results are interpreted in terms of the inter-relationship between NumA1 and PsaA in cell function in Dictyostelium.

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

“…The use of pharmaceuticals is especially valuable in this microorganism when gene knockouts are ineffective (18). Recently, D. discoideum puromycin-sensitive aminopeptidase (Psa) was partially characterized; however, the effects of bestatin which targets this enzyme have not been studied (7).…”

“…Two homologs of mammalian PSA have been identified in D. discoideum and termed PsaA and PsaB (7). An alignment of D. discoideum PsaA with PSA from other species has revealed the presence of a conserved exopeptidase GAMEN motif, a Zn 2ϩ -binding domain, one putative nuclear export signal (NES), and at least one nuclear localization signal (NLS2) (7).…”

“…An alignment of D. discoideum PsaA with PSA from other species has revealed the presence of a conserved exopeptidase GAMEN motif, a Zn 2ϩ -binding domain, one putative nuclear export signal (NES), and at least one nuclear localization signal (NLS2) (7). We previously reported the generation of an anti-PsaA antibody and PsaA-GFP (where GFP is green fluorescent protein) fusion protein-expressing strains (7). With the help of both we have identified that PsaA is distributed mainly throughout the nucleoplasm and to a lesser extent the cytoplasm in growing cells and redistributes throughout the cytoplasm during mitosis.…”

“…We generated a strain expressing PsaA⌬NLS2-GFP, a deletion mutant of PsaA that lacks NLS2. The removal of NLS2 resulted in the inability of PsaA to enter the nucleus and its subsequent accumulation in the cytoplasm in growing and devel-oping cells (7). As in other cells, PsaA may regulate cell cycle progression and cell differentiation in D. discoideum.…”

Novel zinc protease gene isolated from Dictyostelium discoideum is structurally related to mammalian leukotriene A4 hydrolase

“…To date, only 3 proteins in the M1 family have been identified in D. discoideum: 2 homologs of mammalian PSA known as PsaA and PsaB, and LTA4 hydrolase. Furthermore, evidence suggests that PSA regulates the cell cycle and differentiation in D. discoideum (Catalano et al, 2011;Huber and O'Day, 2011). LTA4 hydrolase was found not only in mammalian species but also in several lower vertebrates, including fish and frogs and in some lower species (Pettitt et al, 1991;Strömberg-Kull and Haeggström, 1998).…”