Actin-binding protein involved in actin cytoskeleton regulation and dynamics. Increases the number and size of actin stress fibers and inhibits membrane ruffling. Inhibits actin filament depolymerization. Bundles actin filaments, delays filament nucleation and reduces formation of branched filaments (PubMed:12566430). Plays a role in cholesterol homeostasis. Influences plasma cholesterol levels through regulation of intestinal cholesterol absorption. May act as a scaffold protein by regulating NPC1L1 transportation, an essential protein for cholesterol absorption, to the plasma membrane by recruiting MYO5B to NPC1L1, and thus facilitates cholesterol uptake (By similarity). Interacts with NPCL1; bridges NPC1L1 with MYO5B (PubMed:29880681). Interacts with MYO5B; bridges NPC1L1 with MYO5B (PubMed:29880681). Interacts with PXN; this complex stabilizes actin dynamics (PubMed:24694988). Interacts with F-actin and G-actin (PubMed:12566430). Expressed in the brush border membrane of the small intestine and colocalizes with NPC1L1 and MYO5B (PubMed:29880681). Colocalizes with PXN at focal adhesions in mesangial cells (PubMed:24694988). Colocalizes with actin stress fibers in quiescent cells. PDGF stimulation induced disassembly of stress fibers and formation of peripheral and dorsal ruffles, where LIMA1 is relocalized (By similarity). Highly expressed in placenta, kidney, pancreas, prostate, ovary, spleen and heart. Also detected in lung, liver, brain, skeletal muscle, thymus, testis and intestine. Not detected in leukocytes. Isoform Beta expressed generally at very low levels. Isoform Alpha abundant in epithelial cells from mammary gland, prostate and in normal oral keratinocytes. Low levels in aortic endothelial cells and dermal fibroblasts. Not detectable in myocardium. Down-regulated in some cancer cell lines. Isoform Alpha is induced by serum. Isoform Beta is constitutively expressed. Contains at least 2 actin-binding domains, one on each side of the LIM domain. Both domains bind actin monomers and filaments. The C-terminal domain binds filaments more efficiently than the N-terminus. Phosphorylation of the C-terminal region by MAPK1/MAPK3 reduces its association with F-actin and contributes to actin filament reorganization and enhances cell motility. Genetic variations in LIMA1 influence low density lipoprotein cholesterol (LDL-C) variability and contribute to the low density lipoprotein cholesterol level quantitative trait locus 8 (LDLCQ8) [MIM:618079]. Produced by alternative promoter usage. Produced by alternative promoter usage. Produced by alternative splicing of isoform Beta. Produced by alternative splicing. Extended N-terminus.