Lipid Binding Preferences of the Alternatively Translated Region of PTEN-Long

Abstract

PTEN-Long is a 576-amino acid translational variant of phosphatase and tension homolog on chromosome ten (PTEN), a tumor suppressor gene and antagonist to phosphoinositide-3-kinase (PI3K) signaling. PTEN-Long (PTEN-L) exhibits an alternative translation region (ATR) with an additional 173 N-terminal amino acids at the N-terminal end to the normal PTEN open reading frame. PTEN-L is secreted from cells, can exist outside the cell and shows activity towards PI(3,4,5)P3 after cell entry. Therefore, PTEN-L may have therapeutic uses by restoring a functional tumor suppressor protein to tumor cells. The mechanism by which PTEN-L enters cells is currently not understood. The ATR region of PTEN-L is evolutionary conserved and contains a polyarginine stretch with homology to cell permeable peptides (such as HIV TAT). This suggests that PTEN-L may be able to traverse the plasma membrane passively, but it hasn’t been proven. The N-terminal ATR part of PTEN-L is intrinsically disordered, which we confirmed using CD and FTIR spectroscopy. Our FTIR studies did not reveal any observable structural change of PTEN-L ATR upon lipid binding to PC, PS, PI and PI(4,5)P2 containing vesicles. However, we found that the integrity of model lipid bilayers composed of PS are compromised upon interaction with PTEN-L's ATR and we are further studying this with lipid leakage experiments. The lipid binding preferences of the ATR part of PTEN-L, as well as the full-length protein are being investigated using surface plasmon resonance (SPR). This study aims to gain insight on understanding PTEN-L's ATR membrane interactions at the molecular level.