title: Overexpression of atypical protein kinase C in HeLa cells facilitates macropinocytosis via Src activation.
abstract: Atypical protein kinase C (aPKC) is the first recognized kinase oncogene. However, the specific contribution of aPKC to cancer progression is unclear. The pseudosubstrate domain of aPKC is different from the other PKC family members, and therefore a synthetic peptide corresponding to the aPKC pseudosubstrate (aPKC-PS) sequence, which specifically blocks aPKC kinase activity, is a valuable tool to assess the role of aPKC in various cellular processes. Here, we learned that HeLa cells incubated with membrane permeable aPKC-PS peptide displayed dilated heterogeneous vesicles labeled with peptide that were subsequently identified as macropinosomes. A quantitative membrane binding assay revealed that aPKC-PS peptide stimulated aPKC recruitment to membranes and activated Src. Similarly, aPKC overexpression in transfected HeLa cells activated Src and induced macropinosome formation. Src-aPKC interaction was essential; substitution of the proline residues in aPKC that associate with the Src-SH3 binding domain rendered the mutant kinase unable to induce macropinocytosis in transfected cells. We propose that aPKC overexpression is a contributing factor to cell transformation by interacting with and consequently promoting Src activation and constitutive macropinocytosis, which increases uptake of extracellular factors, required for altered cell growth and accelerated cell migration.
authors.affiliation: Department of Pharmacology, Wayne State University School of Medicine, 540 E. Canfield Ave., 6374 Scott Hall, Detroit, MI 48201, USA. Electronic address: etisdale@med.wayne.edu.
authors.forename: Ellen J
authors.initials: EJ
authors.lastname: Tisdale
authors.affiliation: Department of Physiology, Wayne State University School of Medicine, 540 E. Canfield Ave., 5374 Scott Hall, Detroit, MI 48201, USA.
authors.forename: Assia
authors.initials: A
authors.lastname: Shisheva
authors.affiliation: Department of Pharmacology, Wayne State University School of Medicine, 540 E. Canfield Ave., 6374 Scott Hall, Detroit, MI 48201, USA.
authors.forename: Cristina R
authors.initials: CR
authors.lastname: Artalejo
mesh_terms: D063646:Carcinogenesis / Q000378:metabolism; D002462:Cell Membrane / Q000201:enzymology; D004789:Enzyme Activation; D015870:Gene Expression; D006367:HeLa Cells; D006801:Humans; D010446:Peptide Fragments / Q000378:metabolism / Q000494:pharmacology; D010873:Pinocytosis; D054730:Protein Interaction Domains and Motifs; D011493:Protein Kinase C / Q000235:genetics / Q000378:metabolism*; D047428:Protein Kinase Inhibitors / Q000378:metabolism / Q000494:pharmacology; D021381:Protein Transport; D019061:src-Family Kinases / Q000378:metabolism*
chemical_list: D010446:Peptide Fragments; D047428:Protein Kinase Inhibitors; D019061:src-Family Kinases; C115015:PKC-3 protein; D011493:Protein Kinase C
keywords: Atypical PKC; Macropinocytosis; Pseudosubstrate peptide; Src