title: Molecular characterization of abLIM, a novel actin-binding and double zinc finger protein.
abstract: Molecules that couple the actin-based cytoskeleton to intracellular signaling pathways are central to the processes of cellular morphogenesis and differentiation. We have characterized a novel protein, the actin-binding LIM (abLIM) protein, which could mediate such interactions between actin filaments and cytoplasmic targets. abLIM protein consists of a COOH-terminal cytoskeletal domain that is fused to an NH2-terminal domain consisting of four double zinc finger motifs. The cytoskeletal domain is approximately 50% identical to erythrocyte dematin, an actin-bundling protein of the red cell membrane skeleton, while the zinc finger domains conform to the LIM motif consensus sequence. In vitro expression studies demonstrate that abLIM protein can bind to F-actin through the dematin-like domain. Transcripts corresponding to three distinct isoforms have a widespread tissue distribution. However, a polypeptide corresponding to the full-length isoform is found exclusively in the retina and is enriched in biochemical extracts of retinal rod inner segments. abLIM protein also undergoes extensive phosphorylation in light-adapted retinas in vivo, and its developmental expression in the retina coincides with the elaboration of photoreceptor inner and outer segments. Based on the composite primary structure of abLIM protein, actin-binding capacity, potential regulation via phosphorylation, and isoform expression pattern, we speculate that abLIM may play a general role in bridging the actin-based cytoskeleton with an array of potential LIM protein-binding partners. The developmental time course of abLIM expression in the retina suggests that the retina-specific isoform may have a specialized role in the development or elaboration of photoreceptor inner and outer segments.
authors.affiliation: Berman-Gund Laboratory for the Study of Retinal Degenerations, Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts 02114, USA.
authors.forename: D J
authors.initials: DJ
authors.lastname: Roof
authors.forename: A
authors.initials: A
authors.lastname: Hayes
authors.forename: M
authors.initials: M
authors.lastname: Adamian
authors.forename: A H
authors.initials: AH
authors.lastname: Chishti
authors.forename: T
authors.initials: T
authors.lastname: Li
mesh_terms: D000199:Actins / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001798:Blood Proteins / Q000737:chemistry / Q000235:genetics; D001923:Brain Chemistry; D003001:Cloning, Molecular; D017124:Conserved Sequence; D003598:Cytoskeletal Proteins; D018076:DNA, Complementary; D006801:Humans; D060588:LIM Domain Proteins; D051379:Mice; D008840:Microfilament Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009024:Morphogenesis; D018482:Muscle, Skeletal / Q000737:chemistry; D010750:Phosphoproteins; D011499:Protein Processing, Post-Translational; D011817:Rabbits; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D012160:Retina / Q000737:chemistry* / Q000254:growth & development / Q000378:metabolism; D017948:Retinal Rod Photoreceptor Cells / Q000737:chemistry; D016335:Zinc Fingers
chemical_list: C107440:ABLIM1 protein, human; D000199:Actins; D001798:Blood Proteins; D003598:Cytoskeletal Proteins; C044805:DMTN protein, human; D018076:DNA, Complementary; C489041:Dmtn protein, mouse; D060588:LIM Domain Proteins; D008840:Microfilament Proteins; D010750:Phosphoproteins; D011993:Recombinant Fusion Proteins