IKAP localizes to membrane ruffles with filamin A and regulates actin cytoskeleton organization and cell migration.
Loss-of-function mutations in the IKBKAP gene, which encodes IKAP (ELP1), cause familial dysautonomia (FD), with defective neuronal development and maintenance. Molecular mechanisms leading to FD are poorly understood. We demonstrate that various RNA-interference-based depletions of IKAP lead to defective adhesion and migration in several cell types, including rat primary neurons. The defects could be rescued by reintroduction of wild-type IKAP but not by FD-IKAP, a truncated form of IKAP constructed according to the mutation found in the majority of FD patients. Cytosolic IKAP co-purified with proteins involved in cell migration, including filamin A, which is also involved in neuronal migration. Immunostaining of IKAP and filamin A revealed a distinct co-localization of these two proteins in membrane ruffles. Depletion of IKAP resulted in a significant decrease in filamin A localization in membrane ruffles and defective actin cytoskeleton organization, which both could be rescued by the expression of wild-type IKAP but not by FD-IKAP. No downregulation in the protein levels of paxillin or beclin 1, which were recently described as specific transcriptional targets of IKAP, was detected. These results provide evidence for the role of the cytosolic interactions of IKAP in cell adhesion and migration, and support the notion that cell-motility deficiencies could contribute to FD.
Johansen
Lars Dan
LD
Apoptosis Department and Center for Genotoxic Stress, Institute of Cancer Biology, Danish Cancer Society, Strandboulevarden 49, DK-2100 Copenhagen, Denmark.
Naumanen
Tiina
T
Knudsen
Astrid
A
Westerlund
Nina
N
Gromova
Irina
I
Junttila
Melissa
M
Nielsen
Christina
C
Bøttzauw
Trine
T
Tolkovsky
Aviva
A
Westermarck
Jukka
J
Coffey
Eleanor T
ET
Jäättelä
Marja
M
Kallunki
Tuula
T
D000818:Animals; D002352:Carrier Proteins / Q000032:analysis / Q000037:antagonists & inhibitors / Q000502:physiology*; D002448:Cell Adhesion; D002465:Cell Movement; D022081:Cell Surface Extensions / Q000737:chemistry*; D002478:Cells, Cultured; D002531:Cerebellum / Q000166:cytology; D003285:Contractile Proteins / Q000032:analysis*; D003600:Cytosol / Q000378:metabolism; D064448:Filamins; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D051379:Mice; D008840:Microfilament Proteins / Q000032:analysis*; D009154:Mutation; D009474:Neurons / Q000502:physiology; D051419:Paxillin / Q000032:analysis; D034622:RNA Interference; D016601:RNA-Binding Proteins; D051381:Rats; D022502:Stress Fibers / Q000648:ultrastructure*; D035602:Transcriptional Elongation Factors; D016596:Vinculin / Q000032:analysis
D002352:Carrier Proteins; D003285:Contractile Proteins; C114720:Elp1 protein, human; C491967:Elp1 protein, rat; D064448:Filamins; C491968:Ikbkap protein, mouse; D047908:Intracellular Signaling Peptides and Proteins; D008840:Microfilament Proteins; D051419:Paxillin; D016601:RNA-Binding Proteins; D035602:Transcriptional Elongation Factors; D016596:Vinculin