Identification of H-Ras-Specific Motif for the Activation of Invasive Signaling Program in Human Breast Epithelial Cells

• Published in: Neoplasia (New York, N.Y.) N.Y.), 2011-02, Vol.13 (2), p.98-IN1
• Main Authors: Yong, Hae-Young, Hwang, Jin-Sun, Son, Hwajin, Park, Hae-In, Oh, Eok-Soo, Kim, Hyun-Hwi, Kim, Do Kyun, Choi, Wahn Soo, Lee, Bong-Jin, Kim, Hyeong-Reh Choi, Moon, Aree
• Format: Article
• Language: English
• Subjects: Amino Acid Motifs; Amino Acid Sequence; Breast Neoplasms - metabolism; Breast Neoplasms - pathology; Cell Line, Tumor; Epithelial Cells - metabolism; Epithelial Cells - pathology; Female; Genes, ras; Humans; Molecular Sequence Data; Mutagenesis, Site-Directed; Neoplasm Invasiveness; Oncology; Proline - genetics; Proline - metabolism; Proto-Oncogene Proteins p21(ras) - genetics; Proto-Oncogene Proteins p21(ras) - metabolism; Signal Transduction; Structure-Activity Relationship
• ISSN: 1476-5586; 1522-8002; 1476-5586; 1522-8002
• DOI: 10.1593/neo.101088

Increased expression and/or activation of H-Ras are often associated with tumor aggressiveness in breast cancer. Previously, we showed that H-Ras, but not N-Ras, induces MCF10A human breast epithelial cell invasion and migration, whereas both H-Ras and N-Ras induce cell proliferation and phenotypic transformation. In an attempt to determine the sequence requirement directing the divergent phenotype induced by H-Ras and N-Ras with a focus on the induction of human breast cell invasion, we investigated the structural and functional relationships between H-Ras and N-Ras using domain-swap and site-directed mutagenesis approaches. Here, we report that the hypervariable region (HVR), consisting of amino acids 166 to 189 in H-Ras, determines the invasive/migratory signaling program as shown by the exchange of invasive phenotype by swapping HVR sequences between H-Ras and N-Ras. We also demonstrate that the H-Ras-specific additional palmitoylation site at Cys184 is not responsible for the signaling events that distinguish between H-Ras and N-Ras. Importantly, this work identifies the C-terminal HVR, especially the flexible linker domain with two consecutive proline residues Pro173 and Pro174, as a critical domain that contributes to activation of H-Ras and its invasive potential in human breast epithelial cells. The present study sheds light on the structural basis for the Ras isoform-specific invasive program of breast epithelial cells, providing information for the development of agents that specifically target invasion-related H-Ras pathways in human cancer.