'Servicio de Publicaciones de la Universidad Autonoma de Madrid'
Abstract
Tesis doctoral inédita. Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Biología Molecular. Fecha de lectura: 27-06-08In this work we show that PKCζ plays a key role in the activation of the ERK5 pathway by Gqcoupled
GPCR in epithelial cells and in cardiomyocytes as well as in the induction of cardiac
hypertrophy by agonists acting through Gq-coupled GPCR such as angiotensin II.
Several lines of evidence support the notion that a functional interaction between Gαq and
PKCζ mediates the triggering of the ERK5 cascade by Gq-coupled GPCR. First, ERK5 stimulation by
carbachol or angiotensin II does not appear to require the activity of EGF-Receptors (EGFR) or cytosolic
tyrosine kinases, known to participate in ERK5 activation in response to different mitogens, thus
suggesting that potential GPCR/EGFR transactivation mechanisms are not involved. Second, overexpression
of a constitutively active Gαq subunit mutant promotes “per se” ERK5 stimulation,
independently of its ability to interact with the classical Gαq effector PLCβ. Third, Gαq (and not other
Gα subunits) associates with PKCζ in cells, and co-immunoprecipitation of these endogenous proteins
can be promoted upon Gq-coupled GPCR activation. Moreover, a direct Gαq/PKCζ interaction can be
observed using purified proteins. Fourth, Gαq, PKCζ and MEK5 (the upstream ERK5 activator) are
present in the same multimolecular complex as assessed by co-immunoprecipitation experiments.
Interestingly, Gαq also directly interacts with MEK5, suggesting a scaffold role for this G protein subunit
in the stimulation of this pathway. Finally, stimulation of ERK5 by Gq-coupled GPCR is blocked by
PKCζ pharmacological inhibitors and absent in MEFs or cardiomyocytes derived from PKCζ-deficient
mice. Thus, these data put forward PKCζ as a novel Gαq effector required for ERK5 activation by Gqcoupled
GPCR. Moreover, the finding that PKCζ-deficient mice do not develop angiotensin-induced
cardiac hypertrophy indicates an important physiopathological role for this novel Gαq/PKCζ/ERK5
signaling axis.
In sum, the novel Gαq/PKCζ/ERK5 signal transduction route presented in this study may help
to better understand the mechanisms underlying GPCR-induced cardiac hypertrophy and in the design
of new therapeutic strategies. On the other hand, it opens new avenues to investigate the potential role
of this pathway in other cell types and physiological processes.EL PRESENTE TRABAJO HA SIDO REALIZADO EN EL
DEPARTAMENTO BIOLOGÍA MOLECULAR Y EN EL CENTRO
DE BIOLOGÍA MOLECULAR SEVERO OCHOA (CSIC-UAM)
DE LA FACULTAD DE CIENCIAS DE LA UNIVERSIDAD
AUTÓNOMA DE MADRID, CON LA AYUDA DE UNA BECA
PREDOCTORAL FPI, DEL FONDO DE INVESTIGACIÓN DEL
MINISTERIO DE EDUCACIÓN Y CIENCIA (MEC) Y UN
CONTRATO DE LA RED DE INVESTIGACIÓN COOPERATIVA
EN ENFERMEDADES CARDIOVASCULARES (RECAVA) DEL
INSTITUTO DE SALUD CARLOS III. PARTE DEL TRABAJO
PRESENTADO HA SIDO REALIZADO EN EL DEPARTAMENTO
DE BIOMEDICINA DE LA UNIVERSIDAD DE BERGEN, CON
LA AYUDA DE UNA BECA DE ESTANCIA BREVE DEL FONDO
DE INVESTIGACIÓN DEL MINISTERIO DE EDUCACIÓN Y
CIENCIA (MEC) Y CON LA AYUDA DE UNA BECA DE
ESTANCIA BREVE EMBO CONCEDIDA POR LA EUROPEAN
MOLECULAR BIOLOGY ORGANIZATIONPeer reviewe