Interactions between monomeric CCTS and p150Glued: A novel function for CCTS at the cell periphery distinct from the protein folding activity of the molecular chaperone CCT

Chaperonin containing tailless complex polypeptide 1 (CCT) is a molecular chaperone consisting of eight distinct protein subunits, that when oligomeric is essential for the folding of newly synthesized tubulin and actin. In addition to folding, CCT activity includes functions of individual subunits in their monomeric form. For example, when CCTS monomer levels are increased in cultured mammalian cells, numerous cell surface protrusions are formed from retraction fibres, indicating that an underlying function for the CCTS monomer exists. Here, using a yeast two-hybrid screen we identify the dynactin complex component p150Glued as a binding partner for CCT8 and show by siRNA depletion that this interaction is required for the formation of CCT8-induced cell surface protrusions. Intact microtubules are necessary for the formation of the protrusions, consistent with microtubule minus end transport driving the retraction fibre formation and depletion of either p150Glued or the dynactin complex-associated transmembrane protein dynAP prevents the previously observed localization of GFP-CCT8 to the plasma membrane. Wound healing assays reveal that CCTS monomer levels influence directional cell migration and together our observations demonstrate that in addition to the folding activity of CCT in its oligomer form, a monomeric subunit is associated with events that involve the assembled cytoskeleton.