Filamin a modulates anterior pituitary cell proliferation

TOLEDO J; MUKDSI JH; GUTIÉRREZ S; PÉREZ PA; DE PAUL A; MOYANO CRESPO G; TORRES A

Congreso; Reunión Anual de Sociedades de Biociencias 2019; 2019

Recent studies have identified Filamin A (FLNA) as a scaffold protein that plays vital roles in cellular signalling transduction. Mutations in human FLNA gene have been shown to cause developmental defects and aberrant expression has been observed in many tumours. However, its role in pituitary prolactinoma has seldom been discussed. The aim of this work was to analyse the expression levels of FLNA during pituitary tumour development and to determinate the effect on pituitary cell proliferation. To carry out this objective, female rats treated with estradiol benzoate for 20 (20d), 40 (40d) and 60 (60d) days (hyperplasic/adenomatous pituitary model) and transfected GH3 cells for FLNA overexpression (GH3F+) were used. FLNA expression was determined by Western blot (WB) and subcellular localization was visualized by fluorescence and transmission electron microscopy (TEM). Cell cycle progression was analysed by flow cytometry and ki67 index (proliferation marker) by ICQ. Statistical analysis: ANOVA-Tukey. WB analysis showed two FLNA-immunoreactive bands, at ~280 kDa (full-length) and ~90 kDa, (cleaved form). A weak expression of both isoforms was showed in control, with an increase at 40d and a decrease in latter phase (60d). Furthermore, proliferative phase analysis (S-G2/M) by flow cytometry also revealed a peak at initial stages of with a decrease in latter phases. FLNA subcellular distribution was observed to be mainly cytoplasmic in normal pituitary, whereas 40d was found in cytoplasm and also in nucleus with a specific nucleolus mark. The overexpression of FLNA in GH3 cells significantly decreased Ki67 index. Our results suggest an inhibitory role of FLNA in anterior pituitary cell proliferation as part of the mechanisms that limit cell growth. Furthermore, this conclusion is supported by FLNA nucleus and nucleolus localization at late stages of tumour development. We need further studies to elucidate the mechanistic nature of this phenomenon.