We have now expanded our screen for kinesins involved in podosome regulation and identified the little-characterized kinesin KIF9, a member of the kinesin-9 family (Lawrence et al., 2004). Previously, we could show that kinesin-like family 1C (KIF1C), a kinesin-3 member, is involved in the regulation of podosome dynamics in primary human macrophages (Kopp et al., 2006).
#Reggie level editor for mac plus#
Moreover, microtubules also influence the matrix lytic ability of both podosomes and invadopodia (reviewed in Linder, 2007 Poincloux et al., 2009), which is probably based on the transport of signaling molecules and proteases to sites of degradation (Sakurai-Yageta et al., 2008 Steffen et al., 2008 Wiesner et al., 2010).Īs podosomes are contacted by the plus ends of microtubules (Kopp et al., 2006), transport of material to podosomes is likely to involve plus end–directed motors of the kinesin family. In this context, microtubules function as regulators of podosome dynamics (Kopp et al., 2006 reviewed in Linder, 2009) and their subcellular positioning (Destaing et al., 2005 Ory et al., 2008 McMichael et al., 2010). Podosomes are highly dynamic structures with lifetimes of 2–12 min and show an even higher internal actin turnover (Destaing et al., 2003).īesides their dependence on actin regulation, podosomes are also influenced by microtubules and microtubule-dependent transport processes (Linder et al., 2000b Cougoule et al., 2005). Comparable to focal adhesions (reviewed in Zamir and Geiger, 2001), podosomes have emerged as highly complex organelles that comprise a large variety of components ranging from matrix contact proteins such as integrins (reviewed in Gimona et al., 2008) or CD44 (Chabadel et al., 2007), to adhesion plaque proteins such as talin (Zambonin-Zallone et al., 1989) and paxillin (Pfaff and Jurdic, 2001), to actin regulators such as Arp2/3 complex (Linder et al., 2000a) or cortactin (Webb et al., 2006). Podosomes are constitutively formed in cells that have to cross tissue boundaries, most notably monocytic cells such as monocytes, macrophages, dendritic cells, and osteoclasts (reviewed in Linder and Aepfelbacher, 2003). Podosomes and invadopodia, collectively called “invadosomes,” are matrix contacts with the ability to lyse matrix components and are thus considered as potential key structures of proteolytic cell invasion (reviewed in Gimona et al., 2008 Buccione et al., 2009 Linder, 2009). 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.Ĭells use two strategies for invasion: amoeboid, nonlytic migration through gaps in the extracellular matrix meshwork and mesenchymal, protease-dependent migration involving the cleavage of matrix components (reviewed in Friedl and Wolf, 2003). 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. 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.
Overexpression and microinjection experiments reveal that the unique C-terminal region of KIF9 is crucial for these effects, presumably through binding of specific interactors.
We find that small interfering RNA (siRNA)/short-hairpin RNA–induced knockdown of KIF9 significantly affects both numbers and matrix degradation of podosomes. 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. Besides their dependence on actin regulation, podosomes are also influenced by microtubules and microtubule-dependent transport processes. 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.