PKA, PKC, and the protein phosphatase 2A influence HAND factor function: a mechanism for tissue-specific transcriptional regulation.
The bHLH factors HAND1 and HAND2 are required for heart, vascular, neuronal, limb, and extraembryonic development. Unlike most bHLH proteins, HAND factors exhibit promiscuous dimerization properties. We report that phosphorylation/dephosphorylation via PKA, PKC, and a specific heterotrimeric protein phosphatase 2A (PP2A) modulates HAND function. The PP2A targeting-subunit B56delta specifically interacts with HAND1 and -2, but not other bHLH proteins. PKA and PKC phosphorylate HAND proteins in vivo, and only B56delta-containing PP2A complexes reduce levels of HAND1 phosphorylation. During RCHOI trophoblast stem cell differentiation, B56delta expression is downregulated and HAND1 phosphorylation increases. Mutations in phosphorylated residues result in altered HAND1 dimerization and biological function. Taken together, these results suggest that site-specific phosphorylation regulates HAND factor functional specificity.
Firulli
Beth A
BA
Wells Center for Pediatric Research, James Whitcomb Riley Hospital for Children, 702 Barnhill Drive, Room 2666, Indianapolis, IN 46202, USA.
Howard
Marthe J
MJ
McDaid
Jennifer R
JR
McIlreavey
Leanne
L
Dionne
Karen M
KM
Centonze
Victoria E
VE
Cserjesi
Peter
P
Virshup
David M
DM
Firulli
Anthony B
AB
D000595:Amino Acid Sequence; D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins; D002454:Cell Differentiation / Q000502:physiology; D002460:Cell Line; D002642:Chick Embryo; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D019281:Dimerization; D018507:Gene Expression Regulation, Developmental; D017930:Genes, Reporter; D018257:Helix-Loop-Helix Motifs; D006801:Humans; D008969:Molecular Sequence Data; D009024:Morphogenesis / Q000502:physiology; D010749:Phosphoprotein Phosphatases / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism*; D054648:Protein Phosphatase 2; D021122:Protein Subunits / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D013234:Stem Cells / Q000502:physiology; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D020798:Two-Hybrid System Techniques; D029961:Zebrafish Proteins
D051792:Basic Helix-Loop-Helix Proteins; D017868:Cyclic AMP-Dependent Protein Kinases; D004268:DNA-Binding Proteins; D010749:Phosphoprotein Phosphatases; D011493:Protein Kinase C; D054648:Protein Phosphatase 2; D021122:Protein Subunits; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; D029961:Zebrafish Proteins; C498765:HAND2 protein, human; C410915:hand2 protein, zebrafish; C097341:helix-loop-helix protein, eHAND