Axonal spectrins: all-purpose fences

α-Fodrin in Cytoskeletal Organization and the Activity of Certain Key Microtubule Kinesins

Cortical cytoskeletal proteins are significant in controlling various cellular mechanisms such as migration, cell adhesion, intercellular attachment, cellular signaling, exo- and endocytosis and plasma membrane integrity, stability and flexibility. Our earlier studies involving in vitro and ex vivo approaches led us to identify certain undiscovered characteristics of α-fodrin, a prominent cortical protein. The conventional functions attributed to this protein mainly support the plasma membrane. In the present study, we utilized a global protein expression analysis approach to detect underexplored functions of this protein. We report that downregulation of α-fodrin in glioblastoma cells, U-251 MG, results in upregulation of genes affecting the regulation of the cytoskeleton, cell cycle and apoptosis. Interestingly, certain key microtubule kinesins such as KIF23, KIF2B and KIF3C are downregulated upon α-fodrin depletion, as validated by real-time PCR studies.

βII spectrin (SPTBN1): biological function and clinical potential in cancer and other diseases

βII spectrin, the most common isoform of non-erythrocyte spectrin, is a cytoskeleton protein present in all nucleated cells. Interestingly, βII spectrin is essential for the development of various organs such as nerve, epithelium, inner ear, liver and heart. The functions of βII spectrin include not only establishing and maintaining the cell structure but also regulating a variety of cellular functions, such as cell apoptosis, cell adhesion, cell spreading and cell cycle regulation. Notably, βII spectrin dysfunction is associated with embryonic lethality and the DNA damage response. More recently, the detection of altered βII spectrin expression in tumors indicated that βII spectrin might be involved in the development and progression of cancer. Its mutations and disorders could result in developmental disabilities and various diseases. The versatile roles of βII spectrin in disease have been examined in an increasing number of studies; nonetheless, the exact mechanisms of βII spectrin are still poorly understood. Thus, we summarize the structural features and biological roles of βII spectrin and discuss its molecular mechanisms and functions in development, homeostasis, regeneration and differentiation. This review highlight the potential effects of βII spectrin dysfunction in cancer and other diseases, outstanding questions for the future investigation of therapeutic targets. The investigation of the regulatory mechanism of βII spectrin signal inactivation and recovery may bring hope for future therapy of related diseases.