Abstract
The homeodomain protein PDX-1 is a critical regulator of pancreatic development and insulin production in pancreatic β-cells. We have recently shown that PDX-1 is a substrate of protein kinase CK2; a multifunctional protein kinase which is implicated in the regulation of various cellular aspects, such as differentiation, proliferation, and survival. The CK2 phosphorylation site of PDX-1 is located within the binding region of the E3 ubiquitin ligase adaptor protein PCIF1. To study the interaction between PDX-1 and PCIF1 we used immunofluorescence analysis, co-immunoprecipitation, GST-pull-down studies, and proximity ligation assay (PLA). For the analysis of the stability of PDX-1 we performed a cycloheximide chase. We used PDX-1 in its wild-type form as well as phosphomutants of the CK2 phosphorylation site. In pancreatic β-cells PDX-1 binds to PCIF1. The phosphorylation of PDX-1 by CK2 increases the ratio of PCIF1 bound to PDX-1. The stability of PDX-1 is extended in the absence of CK2 phosphorylation. Our results identified protein kinase CK2 as new important modulator of the stability of PDX-1.
Highlights
Protein kinase CK2 is a multifunctional and pleiotropic protein kinase that plays critical roles in cell differentiation, proliferation, and survival [1,2,3]
We have previously shown that PDX-1 is a substrate for protein kinase CK2 [11]
Since the CK2 phosphorylation site of PDX-1 lies in the middle of the interaction domain with the E3 ubiquitin ligase adaptor protein PCIF1 we wanted to know whether the interaction with and the stability of PDX-1 might be affected by CK2 phosphorylation
Summary
Protein kinase CK2 is a multifunctional and pleiotropic protein kinase that plays critical roles in cell differentiation, proliferation, and survival [1,2,3]. We identified the transcription factor PDX-1 as a new substrate for protein kinase CK2 [11]. We identified two phosphorylation sites for protein kinase CK2 in the C-terminus of PDX-1, namely threonine and serine [11] and found that the transcription factor activity of PDX-1 is modulated by the CK2 phosphorylation. Both phosphorylation sites are in the center of the binding domain for PCIF1 (PDX-1 C terminus interacting factor 1) [20], a protein which targets PDX-1 for ubiquitination and proteasomal degradation [21]. We have analyzed whether the stability of PDX-1 and its interaction with PCIF1 might be affected by the phosphorylation of CK2 within the PCIF1 binding region
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
