Phenylalanine 347 regulates the subcellular localization of PTEN.
PTEN plays diverse tumor-suppressive roles, including inhibition of PI3K-AKT signaling and maintenance of genomic integrity in the nucleus. Elucidating the molecular mechanisms regulating its subcellular localization is therefore essential for understanding PTEN functions. PTEN350, a fragment comprising the N-terminal phosphatase and C2 domains of PTEN, preferentially localizes to the nucleus, although the residues responsible for this localization remain unclear. Previously, we demonstrated that Thr348 contributes to the prominent nuclear accumulation of the PTEN350 fragment and PTENA4 carrying alanine substitutions in the Ser380/Thr382/Thr383/Ser385 (STTS) motif. Since our previous findings suggested that Phe347 also contributes to PTEN nuclear localization, we investigated its role in the present study. Phe347 substitutions (F347A, F347Y, and F347L) were introduced into PTEN and its mutant or truncated derivatives, including PTEN350, PTEN, PTENA4, PTEN350,K13R, and PTENK13R,A4, either alone or in combination with T348D. The F347A substitution significantly attenuated the nuclear accumulation of PTEN350 and PTENA4, whereas F347L partially preserved nuclear accumulation and F347Y substitution exhibited an intermediate phenotype. Similar effects of the F347 substitutions were also observed in the T348D mutants, although the differences among the three substitutions were less pronounced. A similar pattern was observed for the plasma membrane localization of PTEN350,K13R and PTENK13R,A4, with F347A causing the greatest reduction, F347L retaining partial membrane localization, and F347Y exhibiting an intermediate phenotype. The effects of these substitutions were consistently observed in both HEK293T cells and HeLa cells. Collectively, these findings indicate that Phe347 is an important determinant of PTEN subcellular localization.