Characterization of an androgen-responsive, ornithine decarboxylase-related protein in mouse kidney.

Kristian M Silander,Leif C Andersson,Olli A Jänne,Päivi Pihlajamaa,Biswajyoti Sahu

doi:10.1042/bsr20170163

Kristian M Silander, Leif C Andersson + Show 3 more

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https://doi.org/10.1042/bsr20170163

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Journal: Bioscience reports	Publication Date: Jul 12, 2017
Citations: 2	License type: CC BY 4.0

Affiliation: University of Helsinki

Abstract

We have investigated and characterized a novel ornithine decarboxylase (ODC) related protein (ODCrp) also annotated as gm853. ODCrp shows 41% amino acid sequence identity with ODC and 38% with ODC antizyme inhibitor 1 (AZIN1). The Odcrp gene is selectively expressed in the epithelium of proximal tubuli of mouse kidney with higher expression in males than in females. Like Odc in mouse kidney, Odcrp is also androgen responsive with androgen receptor (AR)-binding loci within its regulatory region. ODCrp forms homodimers but does not heterodimerize with ODC. Although ODCrp contains 20 amino acid residues known to be necessary for the catalytic activity of ODC, no decarboxylase activity could be found with ornithine, lysine or arginine as substrates. ODCrp does not function as an AZIN, as it neither binds ODC antizyme 1 (OAZ1) nor prevents OAZ-mediated inactivation and degradation of ODC. ODCrp itself is degraded via ubiquination and mutation of Cys363 (corresponding to Cys360 of ODC) appears to destabilize the protein. Evidence for a function of ODCrp was found in ODC assays on lysates from transfected Cos-7 cells where ODCrp repressed the activity of endogenous ODC while Cys363Ala mutated ODCrp increased the enzymatic activity of endogenous ODC.

Highlights

Polyamines are small ubiquitous aliphatic polycations involved in or are essential for fundamental cellular processes and events ranging from cell growth and proliferation to synthesis, function, and stability of macromolecules
We aligned the sequences of mouse ornithine decarboxylase-related protein (ODCrp), ornithine decarboxylase (ODC), antizyme inhibitor 1 (AZIN1), and antizyme inhibitor 2 (AZIN2) in an attempt to uncover the function of ODCrp
As previously reported by Ivanov et al [24], the following 20 amino acid residues are most critical for the catalytic ODC activity: Lys69 binds pyridoxal-5 -phosphate [31], residues Asp88, Glu94, Arg154, His197, Ser200, Gly235–237, Glu274, Arg277, Asp332, and Tyr389 stabilize the bound pyridoxal-5 -phosphate [7,8], residues Asp332 and Asp361 interact with the substrate [7,32], c 2017 The Author(s)

Summary

Introduction

Polyamines are small ubiquitous aliphatic polycations involved in or are essential for fundamental cellular processes and events ranging from cell growth and proliferation to synthesis, function, and stability of macromolecules. The intracellular polyamine concentration is tightly regulated at the levels of synthesis, catabolism, uptake, and excretion. The cellular ODC activity is regulated by a number of growth- and differentiation-inducing stimuli. As the monomers are rapidly dissociating and reassociating [9], ODC is inactivated and degraded by the polyamine-inducible protein ODC antizyme (OAZ) [10,11,12], which binds ODC monomers and targets them to ubiquitin-independent degradation by 26S proteasome [13,14,15,16,17]. Antizyme inhibitors (AZINs) are ODC-homologous proteins lacking catalytic activity [18]. AZINs, which bind OAZ with a higher affinity than ODC, sequester OAZ, and displace ODC from the ODC–OAZ complex enabling the formation of catalytically active enzyme [19,20]. AZINs that are often induced under same conditions as ODC [21] and are degraded by conventional ubiquitination [22,23]

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