Alternative titles; symbolsCBL3HGNC Approved Gene Symbol: CBLCCytogenetic location: 19q13.32 Genomic coordinates (GRCh38): 19:44,777,854-44,800,651 (from NCB...
Alternative titles; symbols
HGNC Approved Gene Symbol: CBLC
Cytogenetic location: 19q13.32 Genomic coordinates (GRCh38): 19:44,777,854-44,800,651 (from NCBI)
CBL proteins, such as CBLC, are phosphorylated upon activation of a variety of receptors that signal via protein tyrosine kinases. Through interactions with proteins containing SRC (190090) homology-2 (SH2) and SH3 domains, CBL proteins modulate downstream cell signaling (Keane et al., 1999).
▼ Cloning and Expression
By searching an EST database for CBL-like sequences, followed by screening a pancreas carcinoma cell line cDNA library and 5-prime RACE, Keane et al. (1999) cloned CBLC, which they designated CBL3. The deduced 474-amino acid protein has a calculated molecular mass of 52.5 kD. CBLC contains an N-terminal phosphotyrosine-binding domain, a conserved C3HC4 zinc finger motif, and a short proline-rich region near the C terminus. CBLC lacks the extensive proline-rich domain and leucine zipper motif found in CBL (165360) and CBLB (604491). Keane et al. (1999) also identified a splice variant that encodes a protein with a 46-amino acid deletion in the phosphotyrosine-binding domain; this protein has a calculated molecular mass of 47.5 kD. Northern blot analysis detected a 1.7- to 2.0-kb transcript expressed at high levels in liver, pancreas, small intestine, colon, prostate, and trachea. Low expression was detected in stomach, lung, and thyroid, and no expression was detected in hematopoietic tissues. RNA dot blot analysis detected low but ubiquitous expression, with highest levels in adrenal gland and salivary gland in addition to the tissues identified by Northern blot analysis.
By searching an EST database for sequences similar to CBL, followed by screening a kidney cDNA library and oligo capping to extend the 5-prime sequence, Kim et al. (1999) cloned CBLC. Northern blot analysis detected a 2.0-kb transcript highly expressed in colon and small intestine. Expression was also observed in pancreas, placenta, liver, kidney, and prostate, but not in brain, testis, and lymphoid tissues. Minor transcripts of 4.0 and 6.0 kb were also detected in several tissues. Western blot analysis found that endogenous CBLC migrated with an apparent molecular mass of 52 kD in colon carcinoma cell lines.
Griffiths et al. (2003) found that mouse Cblc was expressed in epithelial cells of the gastrointestinal tract, the epidermis, and the respiratory, urinary, and reproductive systems.
▼ Gene Function
By in vitro protein binding assays, Keane et al. (1999) determined that both the long (CBLC-L) and short (CBLC-S) forms of CBLC bound to recombinant fusion proteins containing the SH3 domains of LYN (165120) and CRK (164762), but not with any other SH3-containing proteins. Following EGF (131530) stimulation of cotransfected embryonic kidney cells, CBLC-L, but not CBLC-S, was phosphorylated and immunoprecipitated with EGFR (131550). CBLC-L also inhibited EGF-induced stimulation of transcription by ERK2 (MAPK1; 176948) in a dose-dependent manner. CBLC-S had no effect on MAPK signaling.
Kim et al. (1999) transfected embryonic kidney cells with CBLC and EGFR. The amount of EGFR that coimmunoprecipitated with CBLC increased following EGF stimulation. In vitro binding assays showed that CBLC bound to the SH3 domain, but not the SH2 domain, of FYN (137025), and it bound to the SH3 domain of GRB2 (108355) and the p85 regulatory subunit of phosphatidylinositol 3-kinase (171833). CBLC and FYN coimmunoprecipitated in transfected embryonic kidney cells only when both proteins were present.
▼ Gene Structure
Nau and Lipkowitz (2003) determined that the CBLC gene contains 11 exons and spans about 23 kb. The mouse Cblc gene contains 10 exons and lacks the intron that exists between human exons 8 and 9.
By somatic cell hybrid analysis and radiation hybrid analysis, Keane et al. (1999) mapped the CBLC gene to chromosome 19q13.2. Using FISH, Kim et al. (1999) mapped the CBLC gene to chromosome 19q13.2-q13.3. Southern blot analysis indicated that CBLC is a single copy gene.
▼ Animal Model
Griffiths et al. (2003) found that Cblc-null mice were viable, healthy, and fertile, and displayed no histologic abnormalities up to 18 months of age. Proliferation of epithelial cells in the epidermis and gastrointestinal tracts was unaffected by the loss of Cblc. Moreover, Cblc was not required for attenuation of EGF-stimulated ERK activation in primary keratinocytes.