Dissecting the functional role of PTEN proteins from Physcomitrella patens
Year: 2013
Type: dissertation
Abstract: PTEN (phosphate and tensin homolog) are dual specificity phosphatases with both protein and phosphoinositide phosphatase activity. In animal cells, they hydrolyze PtdIns(3,4,5)P3, a potent second messenger that modulates signaling pathways controlling cell division, cell size, angiogenesis and apoptosis. In addition, PTEN is a relevant gene in animal cells that is often lost in late-stage human tumors, especially those of the brain, prostate and endometrium. Interestingly, PtdIns(3,4,5)P3 is the only known phosphoinositide so far not detected in any plant system, and the enzymes that synthesizes PtdIns(3,4,5)P3 in animal cells do not exist in plants. In this thesis, I have studied PTEN genes in the moss Physcomitrella patens which has emerged as a model system in the last years due to its high frequency of homologous recombination allowing to study functional genomics by gene targeting. In additions, P. patens diverged from the lineage leading to flowering plants 450 million years ago, a feature that places mosses at an evolutionary position that is ideal for comparative studies of the evolution of biological processes in land plants. P. patens genome contains four PTEN genes, named PpPTENA, PpPTENB, PpPTENC and PpPTEND. PpPTEN proteins present the typical organization of PTENs with an N-terminal PTP domain (Protein Tyrosine Phosphatase) and a C-terminal C2-domain.Through protein modeling studies I show that PpPTENA and PpPTEND share high degree of structure similarity with CI_VSP (Ciona intestinales voltage sensor protein) a protein that harbors a transmembrane voltage sensor domain and a cytoplasmic PTEN domain. PpPTENs PTP domain presents the typical catalytic loops seen in the majority of PTENs but their C2 domain is markedly different. In terms of sequence comparison several differences are observed between PpPTENs and HsPTEN, being of main interest differences in the catalytic domain. I characterized a triple ptenb&c&d knockout line and results show that knockout moss plants produced more rhizoids and gametophytes, there is an earlier transition form the protonema juvenile stage to the gametophytic stage and interestingly chloronema and caulonemal cells have a higher growth rate compared to the WT. By using a knock in approach, I have obtained a PpTENB-GFP line to study its localization, revealing that PpPTENB is mostly localized in young growing cells such as chloronema, caulonemal but was well as in the tip of rhizoids.
Author: Rita Matos da Palma Catarino
Language: English
Subfield: Plant Science
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W96426521