The mammalian Staufen protein localizes to the somatodendritic domain of cultured hippocampal neurons: Implications for its involvement in mRNA transport

In hippocampal neurons, certain mRNAs have been found in dendrites (Steward , 1997), and their localization and translation have been implicated in syn aptic plasticity (Martin et al., 1997). One attractive candidate to achieve transport of mRNAs into dendrites is Staufen (Stau), a double-stranded RNA -binding protein, which plays a pivotal role in mRNA transport, localizatio n, and translation in Drosophila (St. Johnston, 1995). Using antibodies rai sed against a peptide located in the RNA-binding domain IIa and a polyclona l antibody raised against a recently cloned human Staufen homolog, we ident ify a 65 kDa rat homolog in cultured rat hippocampal neurons. In agreement with the exclusive somatodendritic localization of mRNAs in these cells, we find that Staufen is restricted to the same domain. By immunoelectron micr oscopy, we show enrichment of the mammalian homolog of Stau (mStau) in the vicinity of smooth endoplasmic reticulum and microtubules near synaptic con tacts. Finally the association of the mStau with neuronal mRNAs is suggeste d by the colocalization with ribonucleoprotein particles specifically in di stal dendrites known to contain mRNA, ribosomes, and translation factors (K nowles et at., 1996). These results suggest a role for mStau in the polariz ed transport and localization of mRNAs in mammalian neurons.