The C. elegans protein, LIN-10, functions in neurons to direct postsynaptic localization of AMPA-type glutamate receptors (AMPARs) and in epithelial cells to direct basolateral localization of the epidermal growth factor receptor (EGFR) protein, LET-23 1,2 . There are three vertebrate homologs of LIN-10: Mint 1, 2, and 3. Sequence comparison between LIN-10 and the Mint proteins, which revealed the presence of a highly divergent amino terminal region, led to the hypothesis that LIN-10 evolved in higher eukaryotes into a family of proteins with distinct cellular functions mediated by their amino terminal domains. To test this hypothesis, the activities of each Mint protein were assayed in lin-10
mutant strains of C. elegans , which display distinct phenotypes for mislocalization of AMPARs and EGFRs. Significantly, of the Mint proteins, only Mint 2 rescued mislocalization of AMPARs, demonstrating that the Mint proteins have distinct activities. Experiments testing the ability of each Mint protein to rescue mislocalization of EGFRs are ongoing and results will be presented. Further functional characterization of the Mint proteins is being performed in a vertebrate system by observing the effects of altered expression of Mint 1 and/or Mint 2 in cultured hippocampal neurons. Preliminary experiments show that a snRNA-mediated approach 3 can be used to attenuate expression of Mint 1 and/or Mint 2 in cultured hippocampal neurons. 1. Rongo, C., Whitfield, C.W., Rodal, A., Kim, S.K., and Kaplan, J.M. (1998) Cell: 94, 751-759. 2. Whitfield, C.W., Benard, C., Barnes, T., Hekimi, S., and Kim, S.K. (1999) Mol Biol Cell: 10, 2087-2100. 3. Akum, B.F., Chen, M., Gunderson, S.I., Riefler, G.M., Scerri-Hansen, M.M., and Firestein, B.L. (2004) Nature Neurosci: 2, 145-152.