Naslov
Filamin A stabilizes thrombopoietin receptor surface expression and inhibits its degradation

Autori
Begonja Jurak, Antonija ; Grozovsky, Renata ; Hoffmeister, Karin ; Falet, Herve ; Hartwig, John

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
Basic and clinical aspects of platelet research including megakaryocytes / - Bischoffsheim, 2014, 25-25

Skup
2nd European Platelet Network (EUPLAN) Conference

Mjesto i datum
Bischoffsheim, Francuska, 24.09.2014. - 26.09.2014

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
filamin, megakaryocytes, cytoskeleton

Sažetak
Introduction. Filamin A (FlnA) is a large cytoplasmic protein that crosslinks actin filament networks and links membrane glycoproteins and signaling proteins to the underlying cytoskeleton. We have previously shown that FlnA is critical for platelet production and survival since mice that specifically lack FlnA in their platelets (FlnA loxP-PF4-Cre) have macrothrombocytopenia, due to rapid platelet clearance and an altered megakaryocyte (MK) maturation program. FlnA loxP-PF4-Cre mice have a marked increase in MK numbers in bone marrow and spleen. Duration and amplitude of thrombopoietin receptor (TPOR, c-Mpl) signaling is a highly regulated process that is crucial for MK differentiation. Methods. We used MKs and platelets from FlnA loxP-PF4-Cre+ mice to study biochemistry of TPOR by flow cytometry, immunofluorescence and Western blot. Results. FlnA loxP-PF4-Cre mice have increased TPO plasma levels and 35% of their circulating platelets are reticulated indicating increased thrombopoiesis. Here we show that TPOR binds to the actin cytoskeleton in bone marrow derived MKs upon TPO stimulation in a dose dependent manner and is inhibited by actin depolymerizing drug, lantranculin A. Linkage of TPOR to the actin cytoskeleton was dependent on FlnA since TPOR was mostly in soluble, F-actin unbound fraction of the cell in FlnA KO MKs. Immunofluorescence analysis revealed partial colocalization of FlnA and TPOR in WT MKs. Moreover, surface expression of TPOR receptor was markedly decreased in both FlnA KO MK and platelets. Prolonged incubation with TPO downregulated TPOR in FlnA KO platelets. This effect was inhibited by lysosome (bafilomycin) and proteasome (MG132) inhibitors. In addition, culturing of FlnA KO MKs with bafilomycin and MG132 rescued surface TPOR expression to normal levels. Conclusion. Our results suggest an important role for FlnA in stabilizing TPOR on the cell surface by linking it to the actin cytoskeleton and preventing its lysosomal and proteasomal degradation.

Izvorni jezik
Engleski

Znanstvena područja
Temeljne medicinske znanosti

POVEZANOST RADA