Filamin B (FlnB) is an actin-binding protein thought to transduce signals from various membrane receptors and intracellular proteins onto the actin cytoskeleton. Formin1 (Fmn1) is an actin-nucleating protein, implicated in actin assembly and intracellular signaling. Human mutations in FLNB cause several skeletal disorders associated with dwarfism and early bone fusion. Mouse mutations in Fmn1 cause aberrant fusion of carpal digits. We report here that FlnB and Fmn1 physically interact, are co-expressed in chondrocytes in the growth plate and share overlapping expression in the cell cytoplasm and nucleus. Loss of FlnB leads to a dramatic decrease in Fmn1 expression at the hypertrophic-to-ossification border. Loss of Fmn1-FlnB in mice leads to a more severe reduction in body size, weight and growth plate length, than observed in mice following knockout of either gene alone. Shortening of the long bone is associated with a decrease in chondrocyte proliferation and an overall delay in ossification in the double-knockout mice. In contrast to FlnB null, Fmn1 loss results in a decrease in the width of the prehypertrophic zone. Loss of both proteins, however, causes an overall decrease in the width of the proliferation zone and an increase in the differentiated hypertrophic zone. The current findings suggest that Fmn1 and FlnB have shared and independent functions. FlnB loss promotes prehypertrophic differentiation whereas Fmn1 leads to a delay. Both proteins, however, regulate chondrocyte proliferation, and FlnB may regulate Fmn1 function at the hypertrophic-to-ossification border, thereby explaining the overall delay in ossification.

• MeSH
• buněčná diferenciace * MeSH
• chondrocyty metabolismus   patologie   MeSH
• fetální proteiny nedostatek   metabolismus   MeSH
• filaminy nedostatek   metabolismus   MeSH
• forminy MeSH
• fyziologická kalcifikace MeSH
• hypertrofie MeSH
• jaderné proteiny nedostatek   metabolismus   MeSH
• lidé MeSH
• mikrofilamentové proteiny nedostatek   metabolismus   MeSH
• myši knockoutované MeSH
• proliferace buněk MeSH
• receptor parathormonu typ 1 metabolismus   MeSH
• růstová ploténka metabolismus   patologie   MeSH
• transport proteinů MeSH
• vazba proteinů MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Research Support, N.I.H., Extramural MeSH
• Názvy látek
• fetální proteiny MeSH
• filaminy MeSH
• forminy MeSH
• jaderné proteiny MeSH
• mikrofilamentové proteiny MeSH
• receptor parathormonu typ 1 MeSH

BACKGROUND: RanBPM (Ran-binding protein in the microtubule-organizing centre) was originally reported as a centrosome-associated protein in human cells. However, RanBPM protein containing highly conserved SPRY, LisH, CTLH and CRA domains is currently considered as a scaffolding protein with multiple cellular functions. A plant homologue of RanBPM has not yet been characterized. RESULTS: Based on sequence similarity, we identified a homologue of the human RanBPM in Arabidopsis thaliana. AtRanBPM protein has highly conserved SPRY, LisH, CTLH and CRA domains. Cell fractionation showed that endogenous AtRanBPM or expressed GFP-AtRanBPM are mainly cytoplasmic proteins with only a minor portion detectable in microsomal fractions. AtRanBPM was identified predominantly in the form of soluble cytoplasmic complexes ~230-500 kDa in size. Immunopurification of AtRanBPM followed by mass spectrometric analysis identified proteins containing LisH and CRA domains; LisH, CRA, RING-U-box domains and a transducin/WD40 repeats in a complex with AtRanBPM. Homologues of identified proteins are known to be components of the C-terminal to the LisH motif (CTLH) complexes in humans and budding yeast. Microscopic analysis of GFP-AtRanBPM in vivo and immunofluorescence localization of endogenous AtRanBPM protein in cultured cells and seedlings of Arabidopsis showed mainly cytoplasmic and nuclear localization. Absence of colocalization with γ-tubulin was consistent with the biochemical data and suggests another than a centrosomal role of the AtRanBPM protein. CONCLUSION: We showed that as yet uncharacterized Arabidopsis RanBPM protein physically interacts with LisH-CTLH domain-containing proteins. The newly identified high molecular weight cytoplasmic protein complexes of AtRanBPM showed homology with CTLH types of complexes described in mammals and budding yeast. Although the exact functions of the CTLH complexes in scaffolding of protein degradation, in protein interactions and in signalling from the periphery to the cell centre are not yet fully understood, structural conservation of the complexes across eukaryotes suggests their important biological role.

• MeSH
• adaptorové proteiny signální transdukční genetika   metabolismus   MeSH
• Arabidopsis chemie   genetika   metabolismus   MeSH
• cytoskeletální proteiny genetika   metabolismus   MeSH
• Eukaryota chemie   klasifikace   genetika   MeSH
• jaderné proteiny genetika   metabolismus   MeSH
• konzervovaná sekvence MeSH
• lidé MeSH
• molekulární evoluce * MeSH
• molekulární sekvence - údaje MeSH
• proteiny huseníčku chemie   genetika   metabolismus   MeSH
• rostliny chemie   klasifikace   genetika   MeSH
• sekvence aminokyselin MeSH
• sekvenční homologie aminokyselin MeSH
• terciární struktura proteinů MeSH
• vazba proteinů MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• adaptorové proteiny signální transdukční MeSH
• cytoskeletální proteiny MeSH
• jaderné proteiny MeSH
• proteiny huseníčku MeSH
• Ran binding protein 9 MeSH Prohlížeč