The association of 14-3-3γ and actin plays a role in cell division and apoptosis in astrocytes

Abstract

The 14-3-3 protein family plays critical regulatory roles in signaling pathways in cell division and apoptosis. 14-3-3γ is mainly expressed in brain. Using primary cultures of cerebral cortical astrocytes, we investigated the relationships between 14-3-3γ proteins and actin in astrocytes in cell division and under ischemia. Our results showed that endogenous 14-3-3γ proteins in immature astrocytes appeared filamentous and co-localized with filamentous actin (F-actin). During certain stages of mitosis, 14-3-3γ proteins first aggregated and then formed a ring-like structure that surrounded the daughter nuclei and enclosed the F-actin. In 4-week-old cultures of astrocytes, 14-3-3γ proteins appeared as punctate aggregates in the cytoplasm. Under ischemia, 14-3-3γ proteins formed filamentous structures and were closely associated with F-actin in surviving astrocytes. However, in apoptotic astrocytes, the intensity of immunostaining of 14-3-3γ proteins in the cytoplasm decreased. The proteins aggregated around the nucleus and dissociated from the actin filaments. Reciprocal co-immunoprecipitations demonstrated that endogenous 14-3-3γ proteins bound to detergent-soluble actin and the level of binding increased after 4 h of ischemia. As actin is a critical structural protein heavily involved in cell division and apoptotic death, our findings suggest that 14-3-3γ proteins play a role in cytoskeletal function during the process of cell division and apoptosis in astrocytes in association with actin.