Nexilin: a novel actin filament-binding protein localized at cell-matrix adherens junction.
We isolated two novel actin filament (F-actin)-binding proteins from rat brain and rat 3Y1 fibroblast. They were splicing variants, and we named brain big one b-nexilin and fibroblast small one s-nexilin. b-Nexilin purified from rat brain was a protein of 656 amino acids (aa) with a calculated molecular weight of 78,392, whereas s-nexilin, encoded by the cDNA isolated from rat 3Y1 cells by the reverse transcriptase-PCR method, was a protein of 606 aa with a calculated molecular weight of 71,942. b-Nexilin had two F-actin- binding domains (ABDs) at the NH2-terminal and middle regions, whereas s-nexilin had one ABD at the middle region because 64 aa residues were deleted and 14 aa residues were inserted in the first NH2-terminal ABD of b-nexilin, and thereby the first ABD lost its activity. b- and s-nexilins bound along the sides of F-actin, but only b-nexilin showed F-actin cross-linking activity. b-Nexilin was mainly expressed in brain and testis, whereas s-nexilin was mainly expressed in testis, spleen, and fibroblasts, such as rat 3Y1 and mouse Swiss 3T3 cells, but neither b- nor s-nexilin was detected in liver, kidney, or cultured epithelial cells. An immunofluorescence microscopic study revealed that s-nexilin was colocalized with vinculin, talin, and paxillin at cell- matrix adherens junction (AJ) and focal contacts, but not at cell-cell AJ, in 3Y1 cells. Overexpressed b- and s-nexilins were localized at focal contacts but not at cell-cell AJ. These results indicate that nexilin is a novel F-actin-binding protein localized at cell-matrix AJ.
Ohtsuka
T
T
Department of Molecular Biology and Biochemistry, Osaka University Medical School, Suita 565-0871, Japan.
Nakanishi
H
H
Ikeda
W
W
Satoh
A
A
Momose
Y
Y
Nishioka
H
H
Takai
Y
Y
D000199:Actins / Q000378:metabolism*; D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D001921:Brain / Q000378:metabolism; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002448:Cell Adhesion; D002460:Cell Line; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D005109:Extracellular Matrix / Q000378:metabolism; D007150:Immunohistochemistry; D007365:Intercellular Junctions / Q000378:metabolism; D008297:Male; D051379:Mice; D008840:Microfilament Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D051381:Rats; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D014018:Tissue Distribution
D000199:Actins; D002352:Carrier Proteins; D018076:DNA, Complementary; C034037:F-actin-binding proteins; D008840:Microfilament Proteins; C116313:Nexn protein, rat; D011994:Recombinant Proteins