Accessory proteins associate with the cytoskeletal filaments to regulate their formation, growth, cross-linking, and cellular functions. These proteins may associate with a specific type of filament. For example, alpha-actinin only binds to actin to form loose bundles. Conversely, others like plakins can cross-link different cytoskeletal filaments, and connect them to the cell junctions on the membrane, like the desmosome. Different accessory proteins can crosslink the same cytoskeletal filaments to generate diverse, complex structures. For example, fascin crosslinks actin filaments into rigid bundles with high mechanical strength, while filamin crosslinks these filaments into a less rigid, gel-like network. Accessory proteins also regulate the assembly or disassembly of cytoskeletal filaments. Proteins like profilin and plus-end tracking proteins, or plus-TIPs, help polymerize microfilaments and microtubules, respectively, while proteins like cofilin and kinesin-thirteen disassemble them.