Cytoskeleton and Nucleotide Signaling in Glioma C6 Cells

Abstract

This chapter describes signaling pathways stimulated by the P2Y(2) nucleotide receptor (P2Y(2)R), that regulate cellular processes dependent on actin cytoskeleton dynamics in glioma C6 cells. P2Y(2)R coupled with G-proteins, in response to ATP or UTP, regulates the level of phosphatidylinositol-4,5-bisphosphate (PIP(2)) which modulates a variety of actin binding proteins and is involved in calcium response and activates Rac1 and RhoA proteins. The RhoA/ROCK signaling pathway plays an important role in contractile force generation needed for the assembly of stress fibers, focal adhesions and for tail retraction during cell migration. Blocking of this pathway by a specific Rho-kinase inhibitor induces changes in F-actin organization and cell shape and decreases the level of phosphorylated myosin II and cofilin. In glioma C6 cells these changes are reversed after UTP stimulation of P2Y(2)R. Signaling pathways responsible for this compensation are connected with calcium signaling. Stimulation of the Rac1 mediated pathway via G(o) proteins needs additional interaction between α(v)β(5) integrins and P2Y(2)Rs. Rac1 activation is necessary for cofilin phosphorylation as well as integrin activation needed for focal complexes formation and stabilization of lamellipodium. Inhibition of positive Rac1 regulation prevents glioma C6 cells from recovery of control cell like morphology.

The Indolinone MAZ51 Induces Cell Rounding and G2/M Cell Cycle Arrest in Glioma Cells without the Inhibition of VEGFR-3 Phosphorylation: Involvement of the RhoA and Akt/GSK3β Signaling Pathways

“…RhoA, one of best-characterized Rho-GTPases, has a key role in regulating the dynamics of actin filaments [22] . Given the morphological and cytoskeletal alterations that are characteristic of RhoA activation ( Fig.…”

“…Removal of MAZ51 led to nearly normal cell cycle progression in cells arrested in G2/M phase, indicating that the MAZ51-induced G2/M phase arrest is reversible. The dynamics of the actin cytoskeleton are involved in controlling cell shape and cell migration and are critical during cell cycle progression and mitosis [22] . Thus, our data suggest a possible link between cell cycle arrest and cytoskeletal alterations, both of which occurred in glioma cells in similar dose- and time-dependent patterns in response to treatment with MAZ51.…”

“…This finding is consistent with those of previous studies, which showed that increases in the activity of RhoA and the resulting activation of its effector, the Rho associated kinase ROCK, induce remodeling of actomyosin; this drives both mitotic rounding and cortical stiffening [25] , [28] , [29] . However, considering that RhoA is the key regulator of actin cytoskeleton dynamics involved in stress fiber formation, cell rounding, and retraction of cell processes [22] , [30] – [36] , it remains to be determined whether the cell rounding induced by MAZ51 is caused by the persistent mitotic cell rounding due to G2/M phase arrest.…”

Caffeine Inhibits Migration in Glioma Cells through the ROCK-FAK Pathway

“…The Rho-family pathway and calcium signaling are two basic systems that regulate the cytoskeleton and cell motility [19]. ROCK inhibition leads to Rac1 activation, which results in increased migration and invasion in human glioma cells [20].…”

Management of cancer pain: 1. Wider implications of orthodox analgesics

“…Second, purinergic and G-protein coupled receptors (eg P2X and P2Y) represent novel targets for analgesics 77,78. These receptors also are involved in cancer 79,80. Third, growth factors can also signal pain, modulate ion channel expression at a hierarchy of levels and can play a significant role in the cancer process itself.…”