The protein 4.1 family includes four well-defined members: erythroid protein 4.1 (4.1R), the bestknown and characterized member, 4.1G (general), 4.1N (neuronal), and 4.1 B (brain). Protein 4.1N is a neuronal homologue of erythrocyte membrane cytoskeletal protein 4.1 (4.1R). Protein 4.1N can stabilize the plasticity of the neuronal membrane via interactions with the spectrin-actin-based skeleton, integral membrane channels and receptors, and membrane-associated guanylate kinases (Diakowski et al. 2006). This brain-specific protein 4.1N isoform intercts with CASK and recruits actin and spectrin (Biederer & Sudhof 2001).