Age-dependent changes in neuronal distribution of CacyBP/SIP: comparison to tubulin and the tau protein

CacyBP/SIP was originally identified as an S100A6 (calcyclin) target and later on as a Siah-1 interacting protein. Recently, we have shown that CacyBP/SIP interacts with tubulin, which suggests its involvement in the reorganization of microtubules. In this work we examined the localization of CacyBP/SIP in cultured neurons and in brain neurons of young and aged rats, and compared this localization with that of tubulin and the tau protein. We have found that in neurons of young rats CacyBP/SIP, tubulin and tau are present in the cytoplasm and in the neuronal processes, whereas in aged animals CacyBP/SIP and tau are mainly seen in the cytoplasm of the neuronal somata. In aged rats, these changes are also accompanied by a different localization pattern of tubulin. Thus, our results show that localization of CacyBP/SIP in brain neurons is similar to that observed for tau and tubulin, which points to the involvement of CacyBP/SIP in cytoskeletal physiology.