The kinesin KIF9 and reggie/flotillin proteins regulate matrix degradation by macrophage podosomes.
Podosomes are actin-based matrix contacts in a variety of cell types, most notably monocytic cells, and are characterized by their ability to lyse extracellular matrix material. Besides their dependence on actin regulation, podosomes are also influenced by microtubules and microtubule-dependent transport processes. Here we describe a novel role for KIF9, a previously little-characterized member of the kinesin motor family, in the regulation of podosomes in primary human macrophages. We find that small interfering RNA (siRNA)/short-hairpin RNA-induced knockdown of KIF9 significantly affects both numbers and matrix degradation of podosomes. Overexpression and microinjection experiments reveal that the unique C-terminal region of KIF9 is crucial for these effects, presumably through binding of specific interactors. Indeed, we further identify reggie-1/flotillin-2, a signaling mediator between intracellular vesicles and the cell periphery, as an interactor of the KIF9 C-terminus. Reggie-1 dynamically colocalizes with KIF9 in living cells, and, consistent with KIF9-mediated effects, siRNA-induced knockdown of reggies/flotillins significantly impairs matrix degradation by podosomes. In sum, we identify the kinesin KIF9 and reggie/flotillin proteins as novel regulators of macrophage podosomes and show that their interaction is critical for the matrix-degrading ability of these structures.
Institute for Medical Microbiology, Virology, and Hygiene, University Medical Center Eppendorf, 20246 Hamburg, Germany Institute for Cardiovascular Diseases, 80336 München, Germany.
Susanne
S
Cornfine
Mirko
M
Himmel
Petra
P
Kopp
Karim
K
El Azzouzi
Christiane
C
Wiesner
Marcus
M
Krüger
Thomas
T
Rudel
Stefan
S
Linder
D018929:Cell Culture Techniques; D022081:Cell Surface Extensions / Q000378:metabolism*; D005109:Extracellular Matrix / Q000378:metabolism*; D006056:Golgi Apparatus / Q000378:metabolism; D006801:Humans; D016547:Kinesins / Q000235:genetics / Q000378:metabolism*; D008264:Macrophages / Q000378:metabolism* / Q000648:ultrastructure; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008870:Microtubules / Q000378:metabolism; D054730:Protein Interaction Domains and Motifs; D055503:Protein Multimerization; D034622:RNA Interference; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism
C435207:KIF9 protein, human; D008565:Membrane Proteins; D011993:Recombinant Fusion Proteins; C106354:flotillins; D016547:Kinesins