Osteoblastic protein tyrosine phosphatases inhibition and connexin 43 phosphorylation by alendronate

Authors
Lezcano, Virginia Alicia; Bellido, Teresita; Plotkin, L. I.; Boland, Ricardo Leopoldo; Morelli, Susana Ana
Publication Year
2014
Language
English
Format
article
Status
Published version
Description
Bisphosphonates (BPs), potent inhibitors of bone resorption which inhibit osteoclasts, have also been shown to act on osteocytes and osteoblasts preventing apoptosis via connexin (Cx) 43 hemichannels and activating the extracellular signal regulated kinases ERKs. We previously demonstrated the presence of a saturable, specific and high affinity binding site for alendronate (ALN) in osteoblastic cells which express Cx43. However, cells lacking Cx43 also bound BPs. Herein we show that bound [3H]-alendronate is displaced by phosphatase substrates. Moreover, similar to Na3VO4, ALN inhibited the activity of transmembrane and cytoplasmic PTPs, pointing out the catalytic domain of phosphatases as a putative BP target. In addition, anti-phospho-tyrosine immunoblot analysis revealed that ALN stimulates tyrosine phosphorylation of several proteins of whole cell lysates, among which the major targets of the BP could be immunochemically identified as Cx43. Additionally, the transmembrane receptor-like PTPs, RPTPµ and RPTPα, as well as the cytoplasmic PTP1B, are highly expressed in ROS 17/2.8 cells. Furthermore, we evidenced that Cx43 interacts with RPTPµ in ROS 17/2.8 and ALN decreases their association. These results support the hypothesis that BPs bind and inhibit PTPs associated to Cx43 or not, which would lead to the activation of signaling pathways in osteoblasts.
Fil: Lezcano, Virginia Alicia. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina
Fil: Bellido, Teresita. Indiana University; Estados Unidos
Fil: Plotkin, L. I.. Indiana University; Estados Unidos
Fil: Boland, Ricardo Leopoldo. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina
Fil: Morelli, Susana Ana. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina
Subject
ALENDRONATE
OSTEOBLASTS
CX43 HEMICHANNELS
PROTEIN TYROSINE PHOSPHATASES
Bioquímica y Biología Molecular
Ciencias Biológicas
CIENCIAS NATURALES Y EXACTAS
Access level
Restricted access
License
https://creativecommons.org/licenses/by-nc-sa/2.5/ar/
Repository
CONICET Digital (CONICET)
Institution
Consejo Nacional de Investigaciones Científicas y Técnicas
OAI Identifier
oai:ri.conicet.gov.ar:11336/21688