Addicsin (Arl6ip5, GTRAP3-18, or JWA,) has many physiological functions by forming hetero-complexes with many factors in the central nervous system (CNS). Recently, several reports demonstrate that addicsin contributes to the development of various neurological diseases. For instance, addicsin affects the formation of chronic morphine dependence, the acquisition of ethanol tolerance, and epilepsy induced by levetiracetam. Moreover, addicsin promotes motor learning and spatial memory. However, molecular functions of addicsin in the formation of these physiological and pathological processes remain largely unknown. To understand molecular mechanism of addicsin, we have tried to clarify addicisn-associated factors by yeast two-hybrid screening. Recently, we identified tomoregulin-1 (TR1) as a novel addicsin-associated factor. TR1, a type I transmembrane protein containing two follistatin-like modules and an epidermal growth factor-like domain, participates in nodal and bone morphogenetic protein signaling.
Here, to clarify a physiological significance of the interaction of addicsin with TR1, we investigated an effect of the interaction of addicsin with TR1 on cell migration by wound-healing assay because the expression of addicsin inhibits tumor cell migration. To evaluate cell migration ability correctly, we have established the stable Flp-In T-REx 293 cell line that expressed addicsin, an addicsin mutant that lacking the TR1-binding region (addicsin-d), TR1, or a TR1 mutant deleting the addicsin-binding region (TR1-d) in a tetracycline-dependent manner. Interestingly, addicsin-d significantly promoted cell migration although addicsin inhibits cell movement. Meanwhile, TR1-d but not wild type of TR1, suppressed cell migration Meanwhile, colony formation assay showed no influence on cell proliferation regardless of the expression of these factors. Furthermore, GM6001, a spectrum of broad matrix metalloproteinase (MMP) inhibitor suppressed the inhibitory effect of addicsin expression on cell migration. These data suggested a possibility that the expression of addicsin inhibits cell migration ability by its association with TR1 mediated through MMP cascade. We would like to discuss a molecular mechanism of addicsin-mediated cell migration.