The function of LIMK1 (LIM domain kinase 1, ENSG00000106683) is as follows. Serine/threonine-protein kinase that plays an essential role in the regulation of actin filament dynamics. Acts downstream of several Rho family GTPase signal transduction pathways (PubMed:10436159, PubMed:11832213, PubMed:12807904, PubMed:15660133, PubMed:16230460, PubMed:18028908, PubMed:22328514, PubMed:23633677). Activated by upstream kinases including ROCK1, PAK1 and PAK4, which phosphorylate LIMK1 on a threonine residue located in its activation loop (PubMed:10436159). LIMK1 subsequently phosphorylates and inactivates the actin binding/depolymerizing factors cofilin-1/CFL1, cofilin-2/CFL2 and destrin/DSTN, thereby preventing the cleavage of filamentous actin (F-actin), and stabilizing the actin cytoskeleton (PubMed:11832213, PubMed:15660133, PubMed:16230460, PubMed:23633677). In this way LIMK1 regulates several actin-dependent biological processes including cell motility, cell cycle progression, and differentiation (PubMed:11832213, PubMed:15660133, PubMed:16230460, PubMed:23633677). Phosphorylates TPPP on serine residues, thereby promoting microtubule disassembly (PubMed:18028908). Stimulates axonal outgrowth and may be involved in brain development (PubMed:18028908). {ECO:0000269|PubMed:10436159, ECO:0000269|PubMed:11832213, ECO:0000269|PubMed:12807904, ECO:0000269|PubMed:15660133, ECO:0000269|PubMed:16230460, ECO:0000269|PubMed:18028908, ECO:0000269|PubMed:22328514, ECO:0000269|PubMed:23633677}. [Isoform 3]: Has a dominant negative effect on actin cytoskeletal changes. Required for atypical chemokine receptor ACKR2- induced phosphorylation of cofilin (CFL1). .