Protein microarray analysis identifies cyclic nucleotide phosphodiesterase as an interactor of Nogo‐A

Nogo‐A, a neurite outgrowth inhibitor, is expressed exclusively on oligodendrocytes and neurons in the CNS. The central domain of Amino‐Nogo spanning amino acids 567–748 in the human Nogo‐A designated NIG, mediates persistent inhibition of axonal outgrowth and induces growth cone collapse by signaling through an as yet unidentified NIG receptor. We identified 82 NIG‐interacting proteins by screening a high‐density human protein microarray composed of 5000 proteins with a recombinant NIG protein as a probe. Following an intensive database search, we selected 12 neuron/oligodendrocyte‐associated NIG interactors. Among them, we verified the molecular interaction of NIG with 2′, 3′‐cyclic nucleotide 3′‐phosphodiesterase (CNP), a cell type‐specific marker of oligodendrocytes, by immunoprecipitation and cell imaging analysis. Although CNP located chiefly in the cytoplasm of oligodendrocytes might not serve as a cell‐surface NIG receptor, it could act as a conformational stabilizer for the intrinsically unstructured large segment of Amino‐Nogo.