In contrast, all mice receiving MGI vector or NRASG12D/C181S-transduced bone marrow cells remained healthy for over one year (Fig

In contrast, all mice receiving MGI vector or NRASG12D/C181S-transduced bone marrow cells remained healthy for over one year (Fig.?1c and data not shown). We sacrificed the moribund mice receiving KRAS4AG12D, KRAS4AG12D/C180S, and NRASG12D-transduced bone marrow cells to examine their disease phenotype. still induces leukemia in Sophocarpine mice, albeit with a much longer latency. Using NRAS/KRAS4A chimeric constructs, we found Mouse monoclonal to CD8/CD38 (FITC/PE) that Sophocarpine the KIKK motif of KRAS4A contributes to the transforming activity of KRAS4A. Mutations at both palmitoylation site and the KIKK motif abolish the ability of oncogenic KRAS4A to induce leukemia in mice. Conclusions Our studies suggest that therapies targeting RAS palmitoylation may also be effective in treating KRAS4A associated malignancies and that interfering the KIKK membrane-targeting motif would enhance the therapeutic effectiveness. genes, which encode four highly homologous proteins: HRAS, NRAS, KRAS4A, and KRAS4B. The latter two are alternative splicing isoforms differing only at the carboxyl terminus. These isoforms possess over 90?% identity in the first 166 amino acid residues (G domain, including switch loops and the binding surfaces for downstream effectors) and are mainly diverse in the carboxyl terminal hypervariable region (HVR). Aberrant activation of the RAS signaling pathway is common in cancer, including 20C30?% cancers with mutations [4]. Among genes, mutations occur most frequently, accounting for 85?% of mutations, followed by (12?%) [4]. mutation is relatively rare (3?%) [4]. Despite of intensive research over three decades, cancers harboring mutations remain the most difficult to treat and are refractory to current targeted therapies [5]. Though strategies to target oncogenic RAS proteins are emerging, identification of alternative targets that block RAS signaling is critical to develop therapies for RAS-driven cancer [6]. The biological activities of RAS rely on post-translation modifications (PTMs) that target RAS proteins to cell membranes, particularly the plasma membrane [7]. One potential approach to block the RAS oncogenic signaling is, therefore, to inhibit RAS translocation to Sophocarpine the plasma membrane. RAS are synthesized as cytosolic proteins. To translocate to membranes, they need first to be Sophocarpine modified by prenylation at the cysteine of the carboxyl terminal CAAX motif by farnesyltransferases (FTase) or geranylgeranyltransferase (GGTase), followed by -AAX proteolysis by RAS converting enzyme (RCE) and methylation of the exposed, farnesylated cysteine residue by isoprenylcysteine carboxyl methyltransferase (Icmt) [8]. CAAX motif is the C-terminal tetrapeptide sequence of RAS proteins (C for cysteine, A for aliphatic amino acid, and X for serine or methionine). Since prenylation of RAS by FTase is the obligate step in RAS PTMs, much emphasis had been placed on developing therapies targeting RAS farnesylation, but successes are modest to date due to a redundancy of the FTase and GGTase [9]. Inhibitors focusing on both FTase and GGTase in combination have been proved too harmful to be clinically useful [10, 11]. The prenylation of RAS proteins provides the minimal signal for his or her membrane association. NRAS, HRAS, and KRAS4A are further palmitoylated by palmitoylacyltransferases (PAT) in the cysteine residue(s) upstream of the CAAX motif [12C14]. On the other hand, KRAS4B, which lacks of cysteine residues at its C terminus to accept palmitoylation changes, traffics directly to the plasma membrane (PM) by associating its positively charged polylysine residues in HVR with the negatively charged component of the inner membrane through electrostatic connection [15, 16]. We have previously demonstrated that palmitoylation is essential for NRAS leukemogenesis, suggesting that focusing on RAS palmitoylation may be an effective therapy for NRAS-related cancers [17]. For cancers with KRAS mutations, much research offers been focused on KRAS4B, since transcript was shown to be more abundant [18]. However, since most oncogenic mutations happen in the G website of RAS, which is definitely identical for KRAS4A and KRAS4B, KRAS4A should be triggered in cancers harboring mutations. Although KRAS4A is definitely dispensable for mouse development [19], accumulating evidences show the modified Sophocarpine ratios may correlate with progression of lung and colorectal adenocarcinoma [20, 21] and that KRAS4A.