Figure 9. Ral GTPases are required for localization of Exocyst to protrusive cell extensions.

(A) Morphology of R3327–5′A or R3327–5′A cells expressing shRNAs targeting RalA or RalB. Note that RNAi mediated reduction of either RalA or RalB suppressed polarized growth of protrusive cell extensions, and cells tended to grow as more tightly compacted colonies than control R3327–5′A prostate tumor cells. (B) Localization of Sec6 and Sec8 in prostate tumor cells is altered following reduction of RalA or RalB expression. R3327–5′A cells or R3327–5′A cells expressing shRNAs targeting RalA or RalB were fixed and labeled with antibodies against Sec6 or Sec8. Note that Exocyst proteins are concentrated in perinuclear compartments, similar to those observed in parental 5′A cells, when RalA expression is reduced. In contrast, these Exocyst subunits accumulate in large cytoplasmic vesicles in cells when RalB expression is reduced.