The PDZ-LIM protein RIL modulates actin stress fiber turnover and enhances the association of alpha-actinin with F-actin.
ALP, CLP-36 and RIL form the ALP subfamily of PDZ-LIM proteins. ALP has been implicated in sarcomere function in muscle cells in association with alpha-actinin. The closely related CLP-36 is predominantly expressed in nonmuscle cells, where it localizes to actin stress fibers also in association with alpha-actinin. Here we have studied the expression and functions of RIL originally identified as a gene downregulated in H-ras-transformed cells. RIL was mostly expressed in nonmuscle epithelial cells with a pattern distinct from that of CLP-36. RIL protein was found to localize to actin stress fibers in nonmuscle cells similarly to CLP-36. However, RIL expression led to partially abnormal actin filaments showing thick irregular stress fibers not seen with CLP-36. Furthermore, live cell imaging demonstrated altered stress fiber dynamics with rapid formation of new fibers and frequent collapse of thick irregular fibers in EGFP-RIL-expressing cells. These effects may be mediated through the association of RIL with alpha-actinin, as RIL was found to associate with alpha-actinin via its PDZ domain, and RIL enhanced the ability of alpha-actinin to cosediment with actin filaments. These results implicate the RIL PDZ-LIM protein as a regulator of actin stress fiber turnover.
Vallenius
Tea
T
Molecular Cancer Biology Program, Institute of Biomedicine and Helsinki University Central Hospital, University of Helsinki, Biomedicum Helsinki, Finland.
Scharm
Burkhard
B
Vesikansa
Aino
A
Luukko
Keijo
K
Schäfer
Reinhold
R
Mäkelä
Tomi P
TP
D000185:Actinin / Q000378:metabolism*; D000199:Actins / Q000378:metabolism*; D000818:Animals; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004847:Epithelial Cells / Q000378:metabolism*; D005347:Fibroblasts / Q000378:metabolism*; D015870:Gene Expression; D005982:Glutathione Transferase / Q000378:metabolism; D049452:Green Fluorescent Proteins; D018398:Homeodomain Proteins / Q000378:metabolism; D006801:Humans; D060588:LIM Domain Proteins; D008164:Luminescent Proteins / Q000378:metabolism; D012516:Osteosarcoma / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D051381:Rats; D011994:Recombinant Proteins / Q000378:metabolism; D013997:Time Factors; D016335:Zinc Fingers
D000199:Actins; D004268:DNA-Binding Proteins; D018398:Homeodomain Proteins; D060588:LIM Domain Proteins; D008164:Luminescent Proteins; C486247:PDLIM4 protein, human; C097168:Pdlim1 protein, rat; C091504:Pdlim4 protein, rat; D011994:Recombinant Proteins; D000185:Actinin; D049452:Green Fluorescent Proteins; D005982:Glutathione Transferase