Phorbol esters promote postsynaptic accumulation of Vesl‐1S/Homer‐1a protein

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Abstract
We examined effects of phorbol esters on the amount and the subcellular distribution of the activity‐regulated protein Vesl‐1S/Homer‐1a in cultured hippocampal neurons. Major Vesl‐1S immunoreactivity (IR) was detected throughout neuronal somata under control conditions. Bath application of phorbol esters, PMA and PDBu resulted in the increase in the amount of Vesl‐1S proteins and promoted punctate distribution of Vesl‐1S IR at the cortical regions of the neuronal somata. Immunofluorescent observations using antisynaptophysin and anti‐Vesl‐1S antibodies, and electron microscopic observations, revealed that Vesl‐1S accumulated at postsynaptic regions following PMA application. Membrane depolarization with high concentrations of external potassium also promoted the punctate distribution of Vesl‐1S IR. These results demonstrate that phorbol‐triggered reaction cascades result in the accumulation of Vesl‐1S protein at postsynaptic regions, and suggest that these phorbol effects may mimic those caused by synaptic activities.