IL-6 is the major growth factor of multiple myeloma (MM). In previous studies we could show that IL-6 induced the activation and tyrosine phosphorylation of Hck nd that Hck was physically associated with gp130 in the multiple myeloma cell line LFM. By studying the coprecipitation of Hck with gp-130 truncation and deletion mutants we identified a 41 amino acid region within gp130 as the binding region for Hck. Deletiori of this region (d 771-811) abrogated Hck binding completely. The Hck binding domahf is surrounded by Y767 and Y814 of gp130, two known STAT3 binding sites. Site directed mutation of Y767 and Y814 showed that these tyrosine residues were not involved in Hck binding. Furthermore, stable transfectants of d 771 -811 revealed a strong decrease in Hck activation and in growth factor induced proliferation compared to wt gp130. In addition, a Src kinase specific inhibitor, PP2, reduced the proliferation of wt gpl30 transfected otlls to basal levels, whereas it showed no effect on proliferaU've signaling of d 771 -811 transfec ted cells. Investigating the downstream signaling events mediated by the Hck-gpl 30 interaction, we were able to show that the phosphorylation of tyrosine kinase Pyk2 was significantly decreased at tyrosine residues 402 and 579 upon stimulation of wt gp130 but not d 771811 transfected cells, indicating that a Pyk2 phosphatase might be involved. Dephosphorylation of Pyk2 is known to block apoptotic signaling. Additionally, phosphorylation of MAPK was induced upon stimulation of wt gp 130, but not of d 771 811, indicating that both Pyk2 and MAPK were downstream signaling componentsl In conclusion, the results demonstrate that gpl 30 stimulation leads to the activation of Éck kinase, which regulates the activity of MAPK and Pyk2 and supports cell growth.
|Original language||English (US)|
|Issue number||11 PART I|
|State||Published - Dec 1 2000|
ASJC Scopus subject areas
- Cell Biology