Kif1c regulates osteoclastic bone resorption as a downstream molecule of p130Cas

Abstract

Podosome formation in osteoclasts is an important initial step in osteoclastic bone resorption. Mice lacking c-Src (c-Src −/− ) exhibited osteopetrosis due to a lack of podosome formation in osteoclasts. We previously identified p130Cas (Crk-associated substrate [Cas]) as one of c-Src downstream molecule and osteoclast-specific p130Cas-deficient (p130Cas ΔOCL−/− ) mice also exhibited a similar phenotype to c-Src −/− mice, indicating that the c-Src/p130Cas plays an important role for bone resorption by osteoclasts. In this study, we performed a cDNA microarray and compared the gene profiles of osteoclasts from c-Src −/− or p130Cas ΔOCL−/− mice with wild-type (WT) osteoclasts to identify downstream molecules of c-Src/p130Cas involved in bone resorption. Among several genes that were commonly downregulated in both c-Src −/− and p130Cas ΔOCL−/− osteoclasts, we identified kinesin family protein 1c (Kif1c), which regulates the cytoskeletal organization. Reduced Kif1c expression was observed in both c-Src −/− and p130Cas ΔOCL−/− osteoclasts compared with WT osteoclasts. Kif1c exhibited a broad tissue distribution, including osteoclasts. Knockdown of Kif1c expression using shRNAs in WT osteoclasts suppressed actin ring formation. Kif1c overexpression restored bone resorption subsequent to actin ring formation in p130Cas ΔOCL−/− osteoclasts but not c-Src −/− osteoclasts, suggesting that Kif1c regulates osteoclastic bone resorption in the downstream of p130Cas (191 words).Significance of the study: We previously showed that the c-Src/p130Cas (Cas) plays an important role for bone resorption by osteoclasts. In this study, we identified Abbreviations: Cas, Crk-associated substrate; CIZ, Cas-interacting zinc-finger protein; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; Kif, kinesin superfamily protein; M-CSF, macrophage colony-stimulating factor; MMP, matrix metalloproteinase; PBS, phosphate-buffered saline; RANKL, receptor activator of NF-κB ligand; TRAP, tartrate-resistant acid phosphatase; α-MEM, α-minimal essential medium.

The osteoclast cytoskeleton – current understanding and therapeutic perspectives for osteoporosis

“…Of note, Myo10 KO osteoclasts derived from The function of kinesins, microtubule-associated motors, is mostly unstudied in osteoclasts thus far. The only published report shows that KIF1C is essential for the formation of the podosome belt (Kobayakawa et al, 2019). This study shows that in osteoclasts, KIF1C, which is in a complex with Src and p130Cas and localized at the podosome belt, is necessary for podosome belt formation.…”

“…This study shows that in osteoclasts, KIF1C, which is in a complex with Src and p130Cas and localized at the podosome belt, is necessary for podosome belt formation. Moreover, KIF1C overexpression increases the resorption activity of osteoclasts and partially compensates for the KO of p130Cas, but not that of Src with regard to podosome belt organization and bone resorption (Kobayakawa et al, 2019). It is not known whether KIF1C is important for the activating phosphorylation of p130Cas and the activation of Rac, as shown for Dock5 (Vives et al, 2011), or it is needed for the interaction between Dock5 and the kinases Src and Pyk2, as shown for p130Cas (Nagai et al, 2013).…”

Tyrosine Kinase Src Is a Regulatory Factor of Bone Homeostasis

“…We, therefore, explored the common downstream molecules of Src and p130Cas, via microarray analysis, using mRNA harvested from osteoclasts derived from Src- and p130Cas-deficient mice. This analysis identified Kif1c, a member of the kinesin superfamily that is transported along with tubulin during cargo transport in the cytoplasm [ 55 ]. The knockdown of Kif1c using shRNA suppressed actin ring formation, suggesting it is essential for actin ring formation downstream of Src and p130Cas [ 55 ].…”

“…This analysis identified Kif1c, a member of the kinesin superfamily that is transported along with tubulin during cargo transport in the cytoplasm [ 55 ]. The knockdown of Kif1c using shRNA suppressed actin ring formation, suggesting it is essential for actin ring formation downstream of Src and p130Cas [ 55 ]. Kif1c regulates actin accumulation at the cell periphery [ 66 ]; therefore, it is implicated in actin ring formation via actin aggregation downstream of Src and p130Cas.…”

“…The expression of these Src-inactivating proteins is low in osteoclasts. Activated Src phosphorylates and activates downstream proteins, such as cortactin [ 46 , 47 , 48 ], p130Cas [ 49 , 50 ], Pyk2 [ 51 , 52 ], Cbl [ 53 ], Vav3 [ 54 ], Kif1c [ 55 ], and plectin [ 56 , 57 ]. These proteins organize the cytoskeleton to form actin rings in osteoclasts.…”