RON Receptor

20 Pages·0.23 MB·English

by  Danilkovitch-Miagkova A., Leonard E.J.

RON Receptor
Alla Danilkovitch-Miagkova* and Edward J. Leonard
Section of Immunopathology, Laboratory of Immunobiology, Division of Basic Sciences,
National Cancer Institute, Frederick Cancer Research and Development Center, Frederick,
MD 21702, USA
*corresponding author tel: [phone], fax: [phone], e-mail: [email protected]
DOI: 10.1006/rwcy.2001.1907.
Chapter posted 5 November 2001
SUMMARY BACKGROUND
RON (Receptuer d’Origine Nantaise) is a transmem- Discovery
brane receptor tyrosine kinase (RTK) that belongsto
the MET receptor tyrosine kinase protein family. Human RON DNA was cloned in 1993 as a result of
RON is expressed in various cell types including screening of cDNA libraries prepared from human
macrophages, osteoclasts, epithelial cells, and hema- tumors and foreskin keratinocytes (Ronsin et al.,
topoietic cells. The RON ligand is macrophage- 1993). Analysis of RON DNA revealed that the gene
stimulating protein (MSP). MSP is a member of the encodes a transmembrane receptor tyrosine kinase
kringle-domain plasminogen-related protein family; structurally similar to the MET receptor kinase
its sequence is similar to that of the MET ligand (Ronsin et al., 1993). A year later the mouse RON
hepatocyte growth factor (HGF). MSP binding to receptor was cloned from purified murine hemato-
RON activates a number of intracellular signaling poietic stem cells (Iwama et al., 1994). The similarity
pathways that mediate MSP biological activities, between RON and MET receptors, and between
includingitseffectsonadhesionandmotility,growth, macrophage-stimulating protein (MSP) and hepato-
differentiation, and survival. MSP/RON-induced cytegrowthfactor(HGF),theMETligand,suggested
cellular responses suggest an important role of RON that MSP might be a RON ligand. This hypothesis
in the regulation of normal cell functions and pos- was proved within 2 years, when it was shown that
sible involvement in various pathological conditions. MSPisindeedtheligandforhumanandmouseRON
Addition of MSP to macrophages expressing RON (Wang et al., 1994b, 1995; Gaudino et al., 1994).
induces shape changes, chemotaxis, macropino-
cytosis, and phagocytosis. RON activation inhibits
generation of nitric oxide (NO) by endotoxin and
thus suppresses endotoxin lethality. RON promotes
Alternative names
adhesion and motility, growth and survival of epi-
thelial cells. Normal RON is overexpressed by a
variety of tumors and transfection of mutated Macrophage-stimulating protein receptor (MSP
forms of RON results in oncogenic transformation. receptor) (Del Gatto et al., 1995). The mouse
Lethality of RON knockout mice reflects the RON receptor is known as STK (stem cell-derived
importance of RON in embryonal development. This tyrosine kinase) (Iwama et al., 1994). According to
review provides a complete RON reference guide the CD nomenclature: CD136 antigen (SwissProt).
showing key points for future directions in RON Official nomenclature for human RON gene:
investigations. MST1R (macrophage stimulating 1 receptor)
CytokineReference Copyright#2001AcademicPress
2 Alla Danilkovitch-Miagkova and Edward J. Leonard
(http://www.ncbi.nlm.nih.gov/LocusLink/list.cgi; Figure 1 Schematic representation of immature (intra-
Angeloni and Lerman, 2001). cellular) and mature (expressed on cell membrane) RON.
RONissynthesizedasa190kDasingle-chainprecursor.It
has a proteolytic cleavage site location in the extracellular
part.TobeexpressedonthecellsurfacetheRONprecursor
Structure
undergoes proteolytic cleavage by enzymes of the endo-
plasmic reticulum. The cleavage converts single-chain
RON is a transmembrane RTK belonging to the immature RON into the (cid:11)(cid:12) disulfide-linked mature RON
MET RTK protein family. The RON gene encodes a heterodimer.
190kDa protein, which is expressed on the cell
surface as a disulfide-linked heterodimer comprising
40kDa (cid:11) and 150kDa (cid:12) chains (Ronsin et al., 1993; α chain
Iwama et al., 1994; Gaudino et al., 1994). The single- 40 kDa
Proteolytic
chain 190kDa pro-RON undergoes intracellular SS
proteolytic cleavage at a basic amino acid site clesaivteage Intracellular part
which converts pro-RON into the mature two-chain proteolytic ar
cleavage ul
heterodimeric receptor (Gaudino et al., 1994). The ell
c
(cid:11) chain of RON is located entirely in the extracel- xtra
lularpartofthereceptor,whereasthe(cid:12)chainconsists E
of an extracellular domain, transmembrane and
Transmembrance
cytoplasmic domains (Figure 1). domain
chain
150 kDA
Main activities and
pathophysiological roles Kinase part
domain c
mi
s
a
The ligand for RON is macrophage-stimulating pl
o
protein (MSP) (Yoshimura et al., 1993), also known yt
C
as hepatocyte growth factor-like protein (HGFL)
(Han et al., 1991). MSP/RON interaction activates
a number of intracellular signaling pathways that Intracellular Disulfide-linked
mediate MSP biological activities. The main targets single chain 190 kDa heterodimeric
immature RON mature RON
and biological activities of MSP/RON are summar-
ized in Table 1.
Chromosome location and linkages
GENE The human RON gene is located on chromosome 3
(region 3p21) (Ronsin et al., 1993). The mouse RON
Accession numbers gene is located on chromosome 9 (R-positive F1
band) (Iwama et al., 1994).
Human RON cDNA: GenBank X70040 (Ronsin
et al., 1993)
PROTEIN
MouseRONcDNA:GenBankX74736(Iwamaetal.,
1994)
IntronicsequencesofthehumanRON:GenBankAF Accession numbers
164633–AF164654 (Angeloni et al., 2000)
Complete coding sequence of the mouse RON: Human RON: SwissProt Q04912
GenBank U65949 (Waltz et al., 1998).
Sequence
Sequence
The RON amino acid sequence is available at
The RON gene sequence is available at GenBank GenBank and Protein Data Bank (http://
(http://www.ncbi.nlm.nih.gov). www.ncbi.nlm.nih.gov).
RON Receptor 3
Table 1 RON targets and biological activities
Targets Biological activity References
Macrophages Shape changes Leonard and Skeel, 1976; Iwama et al., 1995;
Wang et al., 1997; Waltz et al., 1997; Correll et al., 1997;
Nanney et al., 1998;
Chemotaxis in response to C5a Leonard and Skeel, 1976; Skeel and Leonard, 1991, 1994
Chemotaxis Skeel and Leonard, 1980, 1991
Ingestion of EigMC3bi Skeel et al., 1991, 1994;
Iwama et al., 1995
Inhibition of iNOS Wang et al., 1994a, 2000a; Correll et al., 1997;
Chen et al., 1998; Liu et al., 1999
Secretion of IL-6 Leonard and Skeel, unpublished
Macropinocytosis Leonard, unpublished
Epithelial cells Adhesion Willett et al., 1997; Danilkovitch et al., 1999b
Movement Gaudino et al., 1994; Wang et al., 1995, 1996a,
1996b, 2000b; Maggiora et al., 1998;
Montero-Julian et al., 1998;
Danilkovitch et al., 1999b; Chen et al., 2000
Cell scattering Waltz et al., 1997
Ciliary motility Sakamoto et al., 1997
Growth induction Gaudino et al., 1995; Wang et al., 1996a;
Waltz et al., 1997
Growth inhibition Willett et al., 1997
Protection from apoptosis Danilkovitch et al., 2000; Chen et al., 2000.
Apoptosis Willett et al., 1997
Vascular endothelial cells Angiogenesis Cao and Leonard, unpublished
Osteoclasts Bone resorption Kurihara et al., 1996
Growth induction Gaudino et al., 1995
Hematopoietic cells Shape changes Mera et al., 1999
Growth induction Iwama et al., 1996; Mera et al., 1999
Growth inhibition Iwama et al., 1996; Broxmeyer et al., 1996
Cytokine production (IL-6) Banu et al., 1996
Promotion of differentiation Banu et al., 1996
Inhibition of differentiation Broxmeyer et al., 1996
Apoptosis Iwama et al., 1996
Description of protein
The transmembrane domain (amino acid residues
958–982) divides RON into extracellular (amino
Full-lengthhumanRONconsistsof1400aminoacids acid residues 1–957) and intracellular (amino acid
(Ronsin et al., 1993); the murine protein comprises residues 993–1400) regions. In the extracellular part
1378aminoacids(Iwamaetal.,1994).Analysisofthe of RON there are one SEMA (residues 58–507 in
RON amino acid sequence revealed several domains human RON), one plexin or PSI (residues 526–568)
(Figure 2). Because of a high similarity between and four IPT (residues 569–671, 684–767, 770–855,
human and mouse RON receptors, only the human and 874–886) domains (Bork et al., 1999; Angeloni
RON domains are described in detail. et al., 2000). The SEMA domain was initially
4 Alla Danilkovitch-Miagkova and Edward J. Leonard
Figure 2 Structural domains of the human RON receptor.
Y1238
Y1239
Y1353
Y1360
1 2 3 4
SEMA domain (58-507 amino acid residues)
PSI (plexin) domin (526-568 amino acid residues)
IPT domain (1st: 569-671 amino acid residues; 2nd: 684-767 amino acid residues;
3d: 770-855 amino acid residues; 4th: 874-886 amino acid residues)
Transmembrane domain (?)
IPT domain (?)
Proteolytic cleavage site KRRRR (305-309 amino acid residues)
Y1238
Tyrosine residues representing major autophosphorylation site
Y1239
Y1353
Tyrosine residues representing C-terminal multifunctional docking site
Y1360
identified in the semaphorin protein family cysteine residues (Bork et al., 1999). The IPT domain
(Kolodkin et al., 1993; Yu and Kolodkin, 1999). (for immunoglobulin-like fold shared by plexins and
This domain consists of a highly conserved stretch transcriptional factors) has been found in plexins, in
of about 500 amino acids, and is characterized by proteins belonging to the MET family (including
15 conserved cysteines, one conserved potential N- RON) and in the VESPR (the virus-encoded
glycosylation site, and several blocks of conserved semaphoring receptor) (Bork et al., 1999). It seems
residues throughout the domain (Kolodkin et al., that the IPT domain plays a role in neuronal
1993; Yu and Kolodkin, 1999). In addition to development and immunological functions (Bork
semaphorins and RON, the SEMA domain occurs et al., 1999). The PSI and IPT domains might be
in MET (Bork et al., 1999; Comoglio et al., 1999), involved in receptor adhesion through a homo-
neurophilins (Tamagnone et al., 1999), and the philic binding mechanism. The observation that
orphan receptors of the SEX family (Maestrini et al., RON can be expressed on the cell surface as a
1996). One of the proposed functions of the SEMA noncovalently linked dimer (Follenzi et al., 2000)
domain is to mediate protein–protein interactions raises the possibility that this ligand-independent
(Bork et al., 1999). The plexin or PSI (plexins, RON association might be mediated by homophilic
semaphorins, and integrins) domain is approximately interactions between SEMA, PSI, or IPT domains
50 residues in length and usually contains eight of RON.
RON Receptor 5
The intracellular part of RON (983–1400 amino Affinity for ligand(s)
acids) has a catalytic domain (amino acid residues
1073–1335)(Ronsinetal.,1993).Tyrosineresiduesat
MSP, the RON ligand, is a heterodimeric protein
positions 1238 and 1239 represent a RON kinase
consisting of disulfide-linked (cid:11) and (cid:12) chains (Han
autophosphorylation site that is essential for upregu-
et al., 1991; Yoshimura et al., 1993). The calculated
lationofRONcatalyticactivity(Gaudinoetal.,1994;
K is 0.6–0.8nM for the MSP (cid:11)(cid:12) heterodimer and
Longati et al., 1994; Ponzetto et al., 1994). Tyrosines d
1.4nM for its (cid:12) chain (Wang et al., 1997). Despite
1353 and 1360 represent a multifunctional docking
high affinity binding of the (cid:12) chain to RON,
site that plays an important role in RON-mediated
functional studies indicated that only the MSP (cid:11)(cid:12)
signaling (Gaudino et al., 1994; Iwama et al., 1996).
chain heterodimer induced biological responses.
A schematic representation of human RON
Detection of (cid:11) chain binding to RON (Danilkovitch
domain structure is shown in Figure 2.
et al.,1999b)suggeststhat MSP hastwoindependent
A short form of murine RON containing amino
binding sites with high and low affinities located in
acid residues 900–1378was describedby Iwama et al.
the (cid:12) and (cid:11) chain respectively. The calculated EC
(1994). In some human tissues and cell lines a short 50
values are 0.25 and 16.9nM for the (cid:12) and (cid:11) chain,
formofRONhasbeendetectedatthelevelofmRNA
respectively (Danilkovitch et al., 1999a). Ligand–
(Ronsin et al., 1993; Gaudino et al., 1994; Angeloni
receptor interactions are discussed in the chapter on
et al., 2000). It seems that this RON form is an
macrophage-stimulating protein.
alternatively spliced protein (Ronsin et al., 1993).
Mouse cells have an alternative internal promoter
that can drive expression of the short RON protein Cell types and tissues expressing
(Persons et al., 1999). A second promoter in the
the receptor
human RON gene has not yet been found, but since
this region is highly conserved in both mouse and
human genes, it is likely that the alternative internal RON expression has been found in a number of
promoter occurs in the human RON gene. human and rodent cell lines of different origin and in
various human and mouse tissues. Data about RON
expression in cell lines and tissues are summarized
Relevant homologies and species
in Tables 2, 3, 4, 5 and 6 (Only positive data are
differences included.Analysisofdataduringpreparationofthese
tablesrevealedsomediscrepanciesinRONexpression
The sequences of human and mouse RON were by cell lines published by different authors. These
publishedin1993and1994respectively(Ronsinetal., discrepancies can be explained by detection method
1993; Iwama et al., 1994). The amino acid homology limitations and/or by heterogeneity in cell lines
betweenhumanandmouseRonis73.6%intotaland cultured in different laboratories.)
88.6%inthekinasedomain(Iwamaetal.,1994).The RON is also expressed in mouse embryos, which
homology of mouse RON with the mouse MET suggests RON as a regulator of embryonal develop-
protein and the chicken Sea protein is 31.6% and ment. In situ hybridization analysis demonstrated
45% in total, and 65.8% and 70% in the kinase that RON is expressed in the trophoectoderm repre-
domain, respectively (Iwama et al., 1994). The sentingextraembryonictissuesatembryonicdayE3.5
homology of human RON with the human MET (Muraokaetal.,1999).RONexpressioninembryonic
protein is 63% in the kinase domain (Ronsin et al., tissues is detected at E12.5 in the liver and in the
1993). centralnervoussystem(Quantinetal.,1995;Gaudino
Both human and mouse RON bind and can be et al., 1995). At E14.5 RON is detected in the
activated by human MSP (Wang et al., 1994b, 1995; digestive tract epithelium, skin keratinocytes and
Leonard and Danilkovitch, 2000). developingbones(Quantinetal.,1995;Gaudinoetal.,
Chicken Sea might represent the ovian RON 1995).
ortholog but definitive data have not yet been
obtained to support this hypothesis (Huff et al.,
Regulation of receptor expression
1993; Wahl et al., 1999). A RON ortholog has been
identified in Xenopus (Nakamura et al., 1996).
RON has domain structure similarities with other The presence of a number of potential regulatory
members of the MET RTK family, with plexins, elements in the RON promoter (Del Gatto et al.,
VESPR and proteins belonging to the SEX family 1995; Waltz et al., 1998) suggests that RON gene
(Bork et al., 1999). expression may be positively or negatively regulated
6 Alla Danilkovitch-Miagkova and Edward J. Leonard
Table 2 Human cell lines that express RON
Cell line Origin Detection methods References
Bone
GTC-51 Osteoclast-like RT-PCR, FA Gaudino et al., 1995
Bone marrow/hematopoietic
HL-60 Promyelocytic leukemia N Gaudino et al., 1994
K562 Erythroleukemia N Gaudino et al., 1994
W Danilkovitch et al., unpubl.
HEL92 Erythroleukemia W Danilkovitch et al., unpubl.
TF-1 Erythroleukemia W Danilkovitch et al., unpubl.
DAMI Megakaryocytic RT-PCR, FA Banu et al., 1996
CMK Megakaryocytic RT-PCR, FC, FA Banu et al., 1996
Mo7e Megakaryocytic RT-PCR, FC Banu et al., 1996
FA Broxmeyer et al., 1996
CTS Megakaryocytic RT-PCR, FC Banu et al., 1996
Breast
T47D Mammary carcinoma N,W Gaudino et al., 1994
W, FA Collesi et al., 1996
W,FA Maggiora et al., 1998
RT-PCR, FA Gaudino et al., 1995
ZR75.1 Breast carcinoma W, FA Maggiora et al., 1998
Bronchus
BET-1A Bronchial epithelial W, FA, Sakamoto et al., 1997
BEAS-2B Bronchial epithelial W, FA, Sakamoto et al., 1997
Cervix
HeLa Cervix carcinoma W Collesi et al., 1996
Colon
SW620 Adenocarcinoma FC Montero-Julian et al., 1998
W, FA Wang et al., 2000b
DLD-1 Adenocarcinoma W, FA Wang et al., 2000b
HCT116 Adenocarcinoma W, FA Wang et al., 2000b
Colo 201 Adenocarcinoma FC Montero-Julian et al., 1998
RT-PCR, W Chen et al., 2000
W, FA Wang et al., 2000b
HT-29-D4 Adenocarcinoma FC, FA Montero-Julian et al., 1998
HT-29 Adenocarcinoma RT-PCR, W Chen et al., 2000
W, FA Wang et al., 2000b
Kidney
HEK293 Embryonal kidney epithelial W, FA Wang et al., 1997
FA Danilkovitch et al., 1999b
RON Receptor 7
Table 2 (Continued)
Cell line Origin Detection methods References
Liver
HepG2 Hepatocarcinoma FC Montero-Julian et al., 1998
RT-PCR, W, Chen et al., 1997
Lung
H596 Lung carcinoma RT-PCR Willett et al., 1997
H60, Small cell lung cancer RT-PCR Willett et al., 1997
H187 Small cell lung cancer RT-PCR Willett et al., 1997
H249 Small cell lung cancer RT-PCR, FA Willett et al., 1997
H835, H679 Carcinoid cells RT-PCR, FA Willett et al., 1997
H1184, Small cell lung cancer N Angeloni et al., 2000
H2081, Small cell lung cancer (RON expression in cell lines
H1184–H157 was detected by
Angeloni et al., 2000 using N)
H2227 Small cell lung cancer
H1086 Small cell lung cancer
H841 Small cell lung cancer
H69 Small cell lung cancer
H1820 Small cell lung cancer
H660 Small cell lung cancer
H1688 Small cell lung cancer
H446 Small cell lung cancer
H740 Small cell lung cancer
H1373 Non-small cell lung cancer
H1264 Non-small cell lung cancer
H1693 Non-small cell lung cancer
H1944 Non-small cell lung cancer
H838 Non-small cell lung cancer
H1299 Non-small cell lung cancer
H727 Non-small cell lung cancer
H157 Non-small cell lung cancer
H460 Non-small cell lung cancer N Angeloni et al., 2000
RT-PCR Willett et al., 1998
H1466 Non-small cell lung cancer N Angeloni et al., 2000
RT-PCR, Willett et al., 1998
H661 Non-small lung cancer RT-PCR, WB, Willett et al., 1998
H322 Non-small lung cancer RT-PCR Willett et al., 1998
H23 Non-small lung cancer RT-PCR Willett et al., 1998
CaLu1 Non-small lung cancer RT-PCR Willett et al., 1998
ChaGoK1 Non-small lung cancer RT-PCR Willett et al., 1998
EPL65H Non-small lung cancer RT-PCR Willett et al., 1998
8 Alla Danilkovitch-Miagkova and Edward J. Leonard
Table 2 (Continued)
Cell line Origin Detection methods References
H125 Non-small lung cancer RT-PCR Willett et al., 1998
H596 Non-small lung cancer RT-PCR, W, FA Willett et al., 1998
Ovary
SKOV3 Adenocarcinoma W Collesi et al., 1996
NIH:OVCAR3 Adenocarcinoma W Collesi et al., 1996
Pancreas
PT45 Carcinoma W Gaudino et al., 1994
W Collesi et al., 1996
SUIT2 Carcinoma W Gaudino et al., 1994
Rectum
SW837 Adenocarcinoma W, FA Wang et al., 2000b
Skin
SVK14 Keratinocytes FC Montero-Julian et al., 1998
HaCat Keratinocytes FA Danilkovitch et al., 2000
RHEK Keratinocytes BA, WB, FA Wang et al., 1996b
SCC-9 Keratinocytes BA, WB, FA Wang et al., 1996b
HK-NOC Keratinocytes BA, WB, FA Wang et al., 1996a,1996b
FA Danilkovitch et al., 2000
Stomach
MKN-28 Carcinoma N Gaudino et al., 1994
GTL-16 Carcinoma N, W Gaudino et al., 1994
W Collesi et al., 1996
KATO III carcinoma N, W Gaudino et al., 1994
W, FA Collesi et al., 1996
Umbilical cord
HUVEC endothelial W, FA Danilkovitch et al., unpubl.
BA,bindingassay;FA,functionalassays;FC,flowcytometry;N,Northernblotting;RT-PCR,reversetranscriptasepolymerasechain
reaction;W,Westernblotting.
byavarietyofcytokinesandsteroidhormones.Using showed that RON is downregulated during inflam-
human hepatocellular carcinoma cell lines as a model mation by lipopolysaccharide (LPS) or TNF(cid:11) plus
system, it has been shown that HGF, EGF, IL-1, IFN(cid:13) through induction of NO production (Wang
IL-6, TNF(cid:11), serum and PMA can upregulate RON et al., 2000a).
expression (Chen et al., 1997). Upregulation of RON
expression has been detected in epidermal burn
Regulatory Sites and Corresponding Transcriptional
woundandaccessorystructures(Nanneyetal.,1998).
Factors of the RON Gene Promoter
This may be mediated via cytokines and growth
factors present at high concentrations in the wound. Two regions of the mouse RON gene promoter
Investigation of RON expression in macrophages encompassing nucleotides (cid:255)585 to (cid:255)465 and from
RON Receptor 9
Table 3 Rodent cell lines that express RON
Cell line Origin Species Detection methods References
L8057 Megakaryoblastic mouse N Iwama et al., 1994
MEL Erythroid mouse N Iwama et al., 1994
mouse RT-PCR Waltz et al., 1998
DA-1 Il-3-dependent immature mouse N Iwama et al., 1994
BK-1 Keratinocytes mouse BA, W, FA Wang et al., 1996a
BA, FA Wang et al., 1997
MK308 Keratinocytes mouse FA Wang et al., 1996a
BA, FA Wang et al., 1997
SP-1 Keratinocytes mouse FA Wang et al., 1996a
PAM212 Keratinocytes mouse FA Wang et al., 1996a
FA Danilkovitch et al., 2000
CMT-93 Rectum carcinoma mouse FA Waltz et al., 1997
RT-PCR Waltz et al., 1998
YAMC Young adult mouse colon mouse RT-PCR Waltz et al., 1998
XB-2 Teratoma mouse RT-PCR Waltz et al., 1998
NIH3T3 Embryonic fibroblasts mouse RT-PCR Waltz et al., 1998
PC-12 Pheochromocytoma rat RT-PCR, FA Gaudino et al., 1995
BA,bindingassay;FA,functionalassays;N,Northernblotting;RT-PCR,reversetranscriptasepolymerasechainreaction;W,Westernblotting.
(cid:255)465 to (cid:255)285 are important for expression of the whereas several other identified regulatory elements
RON transcript in CMT-93 cells (Waltz et al., 1998). are specific for the mouse or human RON promoter.
The minimal promoter to drive RON expression in In addition to the main RON promoter located
CMT-93 cells is located in the region containing in the 50-flanking region of the gene, a strain-specific
nucleotides from (cid:255)465 to (cid:135)1. Positive regulatory mouse alternative (internal) RON promoter has
elements are located between (cid:255)465 and (cid:255)285 been identified (Persons et al., 1999). This internal
nucleotides.Cell-specificnegativeregulatoryelements promoter is located between exons 10 and 11 of the
may be located between nucleotides (cid:255)585 to (cid:255)465. mouse RON gene, and it contains several consensus
Analysis of the positive regulatory region identified transcription factor binding sites including SP-1,
four copies of the Ets-1 binding sequences, binding Ets, Myb, and GATA-1. The internal promoter
sites for SP-1, AP-1 and AP-2. Ets-1 putative bind- drives expression of truncated mouse RON, the
ing sites are also located in the negative regulatory amino acid sequence of which was published
region. In addition to the above-mentioned regula- previously (Iwama et al., 1994). Although the
tory elements the 50-flanking region of the mouse human RON alternative promoter has not yet been
RON gene contains IFN(cid:11)- and IFN(cid:13)-responsive described, the extremely high homology of this
elements, estrogen, and NF(cid:20)B (Waltz et al., 1998). region between the human and the mouse RON
These data suggest that RON expression may be gene suggests the existence of the alternative promo-
regulated by a variety of cytokines and steroid ter in the human RON gene.
hormones. Analysis of the human RON gene pro-
moter sequence revealed several possible binding
Posttranslational Modification
sites for transcriptional factor, including SP-1,
AP-2, retinoblastoma control elements (RCE), IL-6- The main RON posttranslational modifications
responsive elements (IL-6RE) and GATA-1 (Del include proteolytic cleavage and glycosylation.
Gatto et al., 1995). Thus, some potential transcrip- Both murine and human RON contain eight poten-
tional factor binding sites for SP-1 and AP-2 were tial N-linked glycosylation sites (Ronsin et al., 1993;
identifiedinbothmouseandhumanRONpromoters, Iwama et al., 1994; Gaudino et al., 1994). Ron is
10 Alla Danilkovitch-Miagkova and Edward J. Leonard
Table 4 Human tissues that express RON
Tissue Detection methods References
Lung N Ronsin et al., 1993
N Gaudino et al., 1994
N Sakamoto et al., 1997
Skin N Gaudino et al., 1994
IH Montero-Julian et al., 1998
Colon N Gaudino et al., 1994
N Sakamoto et al., 1997
IH Montero-Julian et al., 1998
Colon mucosa IH, RT-PCR Okino et al., 1999
Small intestine N Sakamoto et al., 1997
IH Montero-Julian et al., 1998
Thymus N Sakamoto et al, 1997
Testis N Sakamoto et al., 1997
Prostate N Sakamoto et al., 1997
Monocytes N Gaudino et al., 1994
PMN N Gaudino et al., 1994
Bone marrow N Gaudinoet al., 1994
Bronchial epithelium IH Sakamoto et al., 1997
Ciliated epithelium of nasal mucosa and oviduct IH Sakamoto et al., 1997
Liver RT-PCR, W Chen et al., 1997
Tonsil IH Montero-Julian et al., 1998
Skin macrophages IF, IH Nanney et al., 1998
Keratinocytes IH, ISH Nanney et al., 1998
Bone marrow megakaryocytes (CD34(cid:135)) RT-PCR, FC, FA Banu et al., 1996
FA Broxmeyer et al., 1996
Osteoclasts FA Kurihara et al., 1996
FA,functionalassays;FC,flowcytometry;IH,immunohistochemistry;ISH,insituhybridization;N,northernblotting;RT,PCR,reverse
transcriptasepolymerasechainreaction;W,westernblotting.
synthesized as a 190kDa single-chain precursor,
Release of soluble receptors
which is converted into mature form by proteolytic
cleavageintheendoplasmicreticulum(Gaudinoetal.,
1994). A conserved site for furin-like proteases (Barr, At present, data concerning release of soluble RON
1991; Mark et al., 1992) is present between residues are unavailable.
305–309 and 307–311 in human and murine
RON precursors respectively (Ronsin et al., 1993;
SIGNAL TRANSDUCTION
Gaudino et al., 1994; Iwama et al., 1994). In cells
expressing physiological amounts of the receptor,
Associated or intrinsic kinases
only mature RON is exposed at the cell surface. In
cells overexpressing transfected RON cDNA, a small
amount of uncleaved protein was found at the cell Interaction of MSP with RON causes receptor
surface (Gaudino et al., 1994). tyrosine phosphorylation and activation (Gaudino