FIP-2, an IκB-Kinase-γ-Related Protein, Is Associated with the Golgi Apparatus and Translocates to the Marginal Band during Chicken Erythroblast Differentiation☆

Abstract Using an antiserum directed against marginal band associated proteins of chicken erythrocytes we isolated clones encoding the chicken homolog of 14.7K-interacting protein 2 (FIP-2), a protein potentially involved in tumor necrosis factor-α/nuclear factor-κB signaling, from a chicken erythroblast cDNA library. We found that chicken FIP-2 was expressed in a variety of tissues and cell types, but unlike its human counterpart, alternative splicing does not appear to take place. Analysis of intracellular localization revealed that FIP-2 was concentrated at the Golgi apparatus in most cells. Perturbation of the Golgi structure without loss of Golgi function (by treatment with nocodazole) resulted in a retention of FIP-2 at the dispersed Golgi fragments. In contrast, disruption of both Golgi structure and function (by brefeldin A) led to a loss of FIP-2 from Golgi membranes. Remarkably, during erythroblast differentiation FIP-2 was found to translocate from the Golgi to the marginal band. Our results support the hypothesis of a function of the Golgi apparatus in signal transduction. Moreover, our results raise the possibility that the marginal band of chicken erythrocytes, in addition to its role in morphogenesis, has a function in signal transduction and that FIP-2 is in some way involved in its formation.