The Upstream Conserved Regions (UCRs) Mediate Homo- and Hetero-oligomerization of Type 4 Cyclic Nucleotide Phosphodiesterases (PDE4s)

Type 4 cyclic nucleotide phosphodiesterases (PDE4s) are divided into long and short forms by the presence or absence of conserved N-terminal domains termed upstream conserved regions (UCRs). We have shown previously that PDE4D2, a short variant, is a monomer, whereas PDE4D3, a long variant, is a dimer. Here, we have determined the apparent molecular weights of various long and short PDE4 variants by size exclusion chromatography and sucrose density gradient centrifugation. Our results indicate that dimerization is a conserved property of all long PDE4 forms, whereas short forms are monomers. Dimerization is mediated by the UCR domains. Given their high sequence conservation, the UCR domains mediate not only homo-oligomerization, but also hetero-oligomerization of distinct PDE4 long forms as detected by co-immunoprecipitation assays and FRET microscopy. Endogenous PDE4 hetero-oligomers are in low abundance, however, compared to homo-dimers revealing the presence of mechanisms that predispose PDE4s towards homo-oligomerization. Oligomerization is a prerequisite for regulatory properties of PDE4 long forms, such as their PKA-dependent activation, but is not necessary for PDE4 protein/protein interactions. As a result, individual PDE4 protomers may independently mediate protein/protein interactions, providing a mechanism whereby PDE4s contribute to the assembly of macromolecular signaling complexes.

Source: BJ Cell - February 21, 2014 Category: Biochemistry Authors: M Xie, B Blackman, C Scheitrum, D Mika, E Blanchard, T Lei, M Conti, W Richter Tags: BJ Signal Source Type: research