Open Accesst‐Darpp is an elongated monomer that binds calcium and is phosphorylated by cyclin‐dependent kinases 1 and 5
Author(s) -
Momand Jamil,
Magdziarz Patrycja,
Feng You,
Jiang Dianlu,
Parga Elizabeth,
Celis Arianna,
Denny Erin,
Wang Xiaoying,
Phillips Martin L.,
Monterroso Estuardo,
Kane Susan E.,
Zhou Feimeng
Publication year - 2017
Publication title -
febs open bio
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.718
H-Index - 31
ISSN - 2211-5463
DOI - 10.1002/2211-5463.12269
Subject(s) - cyclin dependent kinase complex , phosphorylation , kinase , chemistry , protein kinase b , cyclin dependent kinase , phosphoprotein , cyclin dependent kinase 2 , protein kinase a , microbiology and biotechnology , biochemistry , biology , cell cycle , gene
t‐Darpp (truncated isoform of dopamine‐ and cAMP ‐regulated phosphoprotein) is a protein encoded by the PPP 1R1B gene and is expressed in breast, colon, esophageal, gastric, and prostate cancers, as well as in normal adult brain striatal cells. Overexpression of t‐Darpp in cultured cells leads to increased protein kinase A activity and increased phosphorylation of AKT (protein kinase B). In HER 2+ breast cancer cells, t‐Darpp confers resistance to the chemotherapeutic agent trastuzumab. To shed light on t‐Darpp function, we studied its secondary structure, oligomerization status, metal‐binding properties, and phosphorylation by cyclin‐dependent kinases 1 and 5. t‐Darpp exhibits 12% alpha helix, 29% beta strand, 24% beta turn, and 35% random coil structures. It binds calcium, but not other metals commonly found in biological systems. The T39 site, critical for t‐Darpp activation of the AKT signaling pathway, is a substrate for phosphorylation by cyclin‐dependent kinase 1 and cyclin‐dependent kinase 5. Gel filtration chromatography, sedimentation equilibrium analysis, blue native gel electrophoresis, and glutaraldehyde‐mediated cross‐linking experiments demonstrate that the majority of t‐Darpp exists as a monomer, but forms low levels (< 3%) of hetero‐oligomers with its longer isoform Darpp‐32. t‐Darpp has a large Stokes radius of 4.4 nm relative to its mass of 19 kDa, indicating that it has an elongated structure.