PROPRANOLOL BEHAVES AS A BETA-ADRENERGIC AGONIST REORGANIZING ACTIN CYTOSKELETON ON MCF-10A BREAST CELL LINE.

RIVERO E; BUFFONE M; GARGIULO L; DAVIO C; DI SERVI N; BRUZZONE A; LÜTHY IA

Buenos Aires

Jornada; Segundas Jornadas Rioplatenses de Biología; 2018

Sociedad Argentina de Biología - Sociedad Uruguaya de Biociencias

Propranolol (PROP) has been classically classified as a β-blocker, antagonizing β-adrenergic signaling, mainly because of this inhibiting action on protein kinase A and its successful treatment of hypertension. PROP has been proposed as a repurposed drug against breast cancer. Previous results from our laboratory support the hypothesis that PROP sometimes behaves as an agonist, mimicking effect of the agonist Isoproterenol (ISO) on the human breast.The aim of present research was to compare the effect of PROP with those of ISO using the non-tumorigenic breast cell line MCF-10A.PROP (1μM) and ISO (1µM) diminished cell proliferation and increased cell adhesion. PROP was not able to reverse the effect of agonist. Moreover, the effect of PROP and ISO on cell proliferation and cell adhesion was reverted by 10 μM of the pure β2-antagonist ICI-118551, suggesting an agonist effect of PROP.In order to study the agonist action of PROP mainly in cell adhesion, we analyzed the molecular signaling pathways involved in actin cytoskeleton reorganization. The incubation with both ISO and PROP quickly reorganized actin cytoskeleton, increasing the proportion of fibrillar actin. The phosphorylation of LIMP and Cofilin was implied in this effect. The phosphorylation of the latter causes its inactivation, stabilizing in this way actin filaments. This action could be related with the enhancement of actin filaments found by immunofluorescence.The simultaneous incubation with inhibitors of LIMK (as BMS-3) or of a protein involved in LIMK activation as PAK4 (PF3758309) abrogated the effect of both ISO and PROP on cell adhesion, demonstrating the implication of cytoskeleton reorganization on the effect caused by these drugs. On the other hand, ISO and PROP phosphorylated members of the protein family ERM, although their kinetics differed. ISO but not PROP was able to phosphorylate VASP in Ser157, a site phosphorylated by protein kinase A. Even if the mechanisms downstream of beta-adrenergic receptor in this pathway have not yet been uncovered, certain analogs of cAMP are able to activate the same pathway. Concomitantly, ISO was able to enhance cAMP levels while PROP was not.Together, these results suggest that PROP behaves as an agonist in some actions while not in others, suggesting a biased agonist mechanism, not involving the PKA pathway.