| First Author | Wakeham CM | Year | 2019 |
| Journal | J Proteomics | Volume | 206 |
| Pages | 103423 | PubMed ID | 31255707 |
| Mgi Jnum | J:294343 | Mgi Id | MGI:6455399 |
| Doi | 10.1016/j.jprot.2019.103423 | Citation | Wakeham CM, et al. (2019) Identification of PKCalpha-dependent phosphoproteins in mouse retina. J Proteomics 206:103423 |
| abstractText | Adjusting to a wide range of light intensities is an essential feature of retinal rod bipolar cell (RBC) function. While persuasive evidence suggests this modulation involves phosphorylation by protein kinase C-alpha (PKCalpha), the targets of PKCalpha phosphorylation in the retina have not been identified. PKCalpha activity and phosphorylation in RBCs was examined by immunofluorescence confocal microscopy using a conformation-specific PKCalpha antibody and antibodies to phosphorylated PKC motifs. PKCalpha activity was dependent on light and expression of TRPM1, and RBC dendrites were the primary sites of light-dependent phosphorylation. PKCalpha-dependent retinal phosphoproteins were identified using a phosphoproteomics approach to compare total protein and phosphopeptide abundance between phorbol ester-treated wild type and PKCalpha knockout (PKCalpha-KO) mouse retinas. Phosphopeptide mass spectrometry identified over 1100 phosphopeptides in mouse retina, with 12 displaying significantly greater phosphorylation in WT compared to PKCalpha-KO samples. The differentially phosphorylated proteins fall into the following functional groups: cytoskeleton/trafficking (4 proteins), ECM/adhesion (2 proteins), signaling (2 proteins), transcriptional regulation (3 proteins), and homeostasis/metabolism (1 protein). Two strongly differentially expressed phosphoproteins, BORG4 and TPBG, were localized to the synaptic layers of the retina, and may play a role in PKCalpha-dependent modulation of RBC physiology. Data are available via ProteomeXchange with identifier PXD012906. SIGNIFICANCE: Retinal rod bipolar cells (RBCs), the second-order neurons of the mammalian rod visual pathway, are able to modulate their sensitivity to remain functional across a wide range of light intensities, from starlight to daylight. Evidence suggests that this modulation requires the serine/threonine kinase, PKCalpha, though the specific mechanism by which PKCalpha modulates RBC physiology is unknown. This study examined PKCalpha phosophorylation patterns in mouse rod bipolar cells and then used a phosphoproteomics approach to identify PKCalpha-dependent phosphoproteins in the mouse retina. A small number of retinal proteins showed significant PKCalpha-dependent phosphorylation, including BORG4 and TPBG, suggesting a potential contribution to PKCalpha-dependent modulation of RBC physiology. |
