The QKI-6 RNA binding protein localizes with the MBP mRNAs in stress granules of glial cells.

The quaking viable (qk(v)) mouse has several developmental defects that result in rapid tremors in the hind limbs. The qkI gene expresses three major alternatively spliced mRNAs (5, 6 and 7 kb) that encode the QKI-5, QKI-6 and QKI-7 RNA binding proteins that differ in their C-terminal 30 amino acids. The QKI isoforms are known to regulate RNA metabolism within oligodendrocytes, however, little is known about their roles during cellular stress. In this study, we report an interaction between the QKI-6 isoform and a component of the RNA induced silencing complex (RISC), argonaute 2 (Ago2). We show in glial cells that QKI-6 co-localizes with Ago2 and the myelin basic protein mRNA in cytoplasmic stress granules. Our findings define the QKI isoforms as Ago2-interacting proteins. We also identify the QKI-6 isoform as a new component of stress granules in glial cells.