A MITOCHONDRIAL KINASE CASCADE INDUCES ERK PHOSPHORYLATION OF A KEY CHOLESTEROL TRANSPORT PROTEIN

PODEROSO CECILIA; CONVERSO DANIELA; DUARTE ALEJANDRA; NEUMAN ISABEL; MALOBERTI PAULA; CARRERAS MARÍA CECILIA; PODEROSO JUAN; PODESTÁ ERNESTO J

Villa Carlos Paz, Córdoba, Argentina

Congreso; XLIV Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2008

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

ERK1/2 is known to be involved in hormone-stimulated steroid synthesis, but its exact roles and the underlying mechanisms remain elusive. ERK1/2 activation by cAMP results in a maximal steroidogenic rate. We have showed that temporal mitochondrial ERK1/2 activation is obligatory for PKA-mediated steroidogenesis through MEK1/2 phosphorylation in the murine Leydig MA-10 cell line. This cascade of events is strictly dependent on stimuli, hCG/cAMP/PKA leads to the phosphorylation of a constitutive mitochondrial MEK1/2 and ERK1/2 pool. ERK1 specifically co-precipitates with a 30kDa mitochondrial form of StAR which presents a basic-hydrophobic motif shared in several ERK substrates and mitochondrial 30kDa StAR interacts with VDAC (voltage-dependent anionic channel). ERK1/2 phosphorylates StAR at Ser232 only in the presence of cholesterol. Mutagenesis of Ser232 to Ala (S232A) inhibited in  vitro StAR phosphorylation by active ERK1/2. Transient  transfection of MA-10 cells with S232A reduced the yield of steroids. We show that StAR is a novel substrate of mitochondrial ERK that is part of a multimeric kinase complex that regulates cholesterol transport. StAR phosphorylated at Ser232 may acquire additional negative charges and associate with VDAC promoting the retention of the mature form of 30kDa StAR in the outer mitochondrial membrane and to the formation of the multiprotein in  vitro StAR phosphorylation by active ERK1/2. Transient  transfection of MA-10 cells with S232A reduced the yield of steroids. We show that StAR is a novel substrate of mitochondrial ERK that is part of a multimeric kinase complex that regulates cholesterol transport. StAR phosphorylated at Ser232 may acquire additional negative charges and associate with VDAC promoting the retention of the mature form of 30kDa StAR in the outer mitochondrial membrane and to the formation of the multiprotein StAR phosphorylation by active ERK1/2. Transient  transfection of MA-10 cells with S232A reduced the yield of steroids. We show that StAR is a novel substrate of mitochondrial ERK that is part of a multimeric kinase complex that regulates cholesterol transport. StAR phosphorylated at Ser232 may acquire additional negative charges and associate with VDAC promoting the retention of the mature form of 30kDa StAR in the outer mitochondrial membrane and to the formation of the multiprotein