In vitro interaction of tubulin with the photoreceptor cGMP phosphodiesterase γ-subunit

The α and β tubulins compose the microtubule cytoskeleton which is involved in many cellular processes such as vesicular transport. The photoreceptor cells in the retina are neurons specialized for phototransduction. Here we report a novel interaction between tubulin and the photoreceptor cGMP phosphodiesterase (PDE6) gamma subunit (PDEγ). The specificity and molecular details of the PDEγ:tubulin interaction were analyzed through the experiments of pull down, microtubule co-sedimentation, and NMR spectroscopy. The tubulin-interacting site was identified to be in the PDEγ C-terminal I67-G85 region, and the interaction interface appeared to be distinct from those with the other PDEγ targets in phototransduction. We also observed that PDEγ interacted with tubulin in a GTP-dependent manner. Our findings offer implications for non-phototransduction role(s) of PDEγ in the photoreceptor neurons.