Oncostatin M

14 Pages·0.786 MB·English

by  Bruce A.G., Rose T.M.

Oncostatin M
A. Gregory Bruce and Timothy M. Rose
*
Department of Pathobiology, School of Public Health and Community Medicine,
University of Washington, Box 357238, Seattle, WA 98195, USA
*corresponding author tel: [phone], fax: [phone], e-mail: [email protected]
DOI: 10.1006/rwcy.2000.06005.
SUMMARY Structure
Oncostatin M (OSM) is a pleiotropic cytokine within Human OSM is a secreted glycoprotein which is
the IL-6 family of cytokines which regulates cell initially translated as a 252 amino acid polypeptide
growth and differentiation in a wide variety of bio- with a 25 residue hydrophobic signal sequence at the
logicalsystems,includinghematopoiesis,neurogenesis, N-terminus that is removed during the secretion pro-
and osteogenesis. cess.Anadditionalposttranslationalcleavageremoves
31 C-terminal residues, resulting in a 192 amino acid
disulfide-linked mature protein. OSM adopts a four
BACKGROUND
(cid:11)-helical bundle structure with up-up-down-down
topology similar to that determined for other cyto-
Discovery kines and growth factors (Rose and Bruce, 1991;
Robinson et al., 1994).
Oncostatin M (OSM) was originally discovered as a
protein which inhibited the proliferation of a number
of human tumor cell lines, but not normal human Main activities and
fibroblasts. It was isolated from supernatants of U-
pathophysiological roles
937 human histiocytic leukemia cells that were
induced to differentiate into macrophage-like cells
by treatment with phorbol 12-myristate 13-acetate OSM has been shown to be a pleiotropic cytokine
(PMA)(Zarlingetal.,1986).Human,simian,bovine, which regulates cell growth and differentiation in a
and murine forms of OSM have been cloned and wide variety of biological systems including hemato-
characterized. OSM has been shown by sequence poiesis, neurogenesis, and osteogenesis (Bruce et al.,
homology and structural and functional similarities 1992b). The elaboration of the biological activities of
to be closely related to leukemia inhibitory factor OSM has been confounded by the presence of
(LIF) and other members of the IL-6 family of different OSM receptor signaling systems in humans
cytokines, including IL-6, IL-11, ciliary neurotropic and mice. In humans, OSM signals through two
factor (CNTF), and cardiotropin 1 (CT-1) (Bazan, different receptors complexes; the LIF/OSM shared
1991; Rose and Bruce, 1991). receptor (Gearing and Bruce, 1992), which shares
high-affinity binding with LIF, an evolutionarily
related protein with structural similarity to OSM
Alternative names
(Rose and Bruce, 1991), and the OSM-specific
receptor which binds OSM uniquely (Bruce et al.,
A number of abbreviations for oncostatin M have 1992b).Inmice,OSMsignalsonlythroughthemurine
been used in the literature, including OSM, OM, homologoftheOSM-specificreceptor(Ichiharaetal.,
Onco M, and ONC, although OSM is the preferred 1997; Lindberg et al., 1998). To confuse matters,
abbreviation. There are no other factors that have human OSM, used historically for in vitro and in vivo
subsequently been shown to be OSM. studies in mice, binds uniquely to the murine LIF
586 A. Gregory Bruce and Timothy M. Rose
Table 1 OSM gene sequences
Species Accession number Source Type Size (bp) References
Human M27286 Brain Gene, exon 1/intron 1 junction 65 Malik et al., 1989
M27287 Brain Gene, exon 2/intron 1 and 2 junctions 155 Malik et al., 1989
M27288 Brain Gene, exon 3/intron 2 junction 1,643 Malik et al., 1989
AC004264 Gene locus 47,188 Unpublished
Mouse D31942 Pre-B cell mRNA, complete 1,848 Yoshimura et al., 1996
Not deposited Promoter region 867 Yoshimura et al., 1996
Bovine S78434 Gene, exon 1 67 Malik et al., 1995
S78487 Gene, exon 2 152 Malik et al., 1995
S78435 Gene, exon 3 903 Malik et al., 1995
Table 2 OSM gene structure
receptorandthusexhibitsonlythebiologicalactivities
Properties Human Murine Bovine
of LIF in mice and not that of OSM receptor OSM OSM OSM
(Ichihara et al., 1997; Lindberg et al., 1998).
Therefore, the biological activities for OSM are Gene size (cid:24)5kbp nd (cid:24)5kbp
derived from signaling through two different recep-
mRNA size (cid:24)2kbp (cid:24)2kbp nd
torsandoverlapthoseofLIFinhumanbutnotmurine
Intron number 2 2 2
systems. The ability of OSM to function through the
OSM-specific and LIF/OSM shared receptors in Exon 1, noncoding (cid:24)25bp (cid:24)52bp nd
humans and only the OSM-specific receptor in mice Exon 1, coding 34bp 31bp 34bp
suggests that there may be significant differences in
Intron 1 1,620bp nd 1,418bp
the biological roles played by OSM in different
Exon 2, coding 143bp 137bp 134bp
species. Furthermore, although the biological activity
ofOSMhasbeenstudiedinvariousinvitroassays,its Intron 2 534bp nd 572bp
exact role in vivo has not been established. As such, Exon 3, coding 582bp 621bp 567bp
the literature on OSM should be reviewed with
Exon 3, noncoding 1,054bp 1,018bp nd
careful consideration of these findings.
nd,notdetermined.
GENE AND GENE REGULATION
portion of the mature molecule. The last exon con-
Accession numbers
tains the remaining coding sequences and all of the
30 noncoding sequences. The 30 ends ofthe OSM
The OSM genes and mRNA transcripts have been cDNAs contain an A(cid:135)T-rich region with several
cloned and characterized from human, simian, ‘ATTTA’ pentamer motifs, which are involved in the
murine, and bovine sources (Table 1). The OSM regulation of the stability of many cytokine and
genes span approximately 5kb and transcripts of lymphokine transcripts. The intron–exon structure is
approximately 2kb have been detected in various identical between the human, murine, and bovine
tissues (see below). Three exons have been identified genes (Table 2).
in the OSM gene and the intron–exon junction se-
quences conform to the GT...AT rule for nucleotides
Sequence
flanking eukaryotic exon boundaries. The first exon
containsthe50 noncodingDNAandtheDNAencod-
ing the initiating methionine and 10 amino acids of For the nucleotide sequence of human OSM, see
the signal sequence. The second exon encodes the Figure1, ofmurineOSM,seeFigure2, andofbovine
remainder of the signal sequence and the first OSM, see Figure 3.
Oncostatin M 587
Figure 1 The nucleotide and encoded amino acid sequence of human OSM.
Thesignalsequenceisboxedingreen.(Fullcolourfiguremaybeviewedonline.)
Chromosome location
related LIF gene (Rose et al., 1993). The OSM gene
hasalsobeencolocalizedwiththeLIFgeneonmouse
In humans, the OSM gene has been localized to chromosome 11, which is syntenic in this region with
chromosome 22 at 22q12 just upstream of the closely human chromosome 22 (Yoshimura et al., 1996).
588 A. Gregory Bruce and Timothy M. Rose
Figure 2 The nucleotide and encoded amino acid sequence of murine OSM.
Thesignalsequenceisboxedingreen.(Fullcolourfiguremaybeviewedonline.)
Relevant linkages
telomeric to centromeric, with the OSM gene located
upstream of the LIF gene. The OSM and LIF genes
The OSM and LIF genes are tandemly arranged on were also found to be within 2cM of each other on
human chromosome 22 in the same transcriptional murine chromosome 11. These findings provide
orientation separated by approximately 10kb (Rose strong evidence that OSM and LIF genes resulted
et al., 1993). The direction of gene transcription is from duplication of a common ancestral gene.
Oncostatin M 589
Figure 3 The nucleotide and encoded amino acid sequence of bovine OSM.
Thesignalsequenceisboxedingreen.(Fullcolourfiguremaybeviewedonline.)
Regulatory sites and corresponding Cells and tissues that express
transcription factors the gene
ThemajorinitiationsiteofthemurineOSMgenewas There are only a few studies describing cell typesthat
found at (cid:255)52 with a minor initiation site at (cid:255)81. No produceOSM.OSMwasfirstidentifiedinthehuman
TATA box was found; however, there is a GC-rich myelocytic leukemia cell line U937, after treatment
region near the transcription initiation site. A IFN(cid:13)- with phorbol esters. Subsequent studies identified
activated site (GAS) like sequence, ‘TTCCCAGAA’, activated T lymphocytes and macrophages, cell cul-
found at (cid:255)100 is identical to that of the human Fc(cid:13) tures derived from acquired immunodeficiency virus
receptorgenepromoterandthe rat(cid:11) -macroglobulin (AIDS)-related Kaposi’s sarcoma (Nair et al., 1992)
2
promoter. This sequence appears to be involved in and retrovirus-infected CD4(cid:135) T cells (Radka et al.,
activation of the murine OSM promoter by binding 1993) as sources of OSM mRNA. Murine OSM
STAT5, which is activated by IL-2, IL-3, and EPO. mRNAhasbeendetectedinbonemarrowandspleen
Another GAS-like sequence, ‘TTCGAAGAA’, was but was not detectable in liver, lung, ovary, small
found at (cid:255)180 but does not appear to be involved in intestine, kidney, or brain (Yoshimura et al., 1996).
promoter activation by STAT5. Additionally, murine OSM has been detected in
590 A. Gregory Bruce and Timothy M. Rose
the gonads of developing embryos (Hara et al., Sequence
1998).
For the amino acid sequence of human OSM, see
PROTEIN
Figure1,ofmurineOSM,seeFigure2,andofbovine
Accession numbers OSM, see Figure 3. A comparison of the human,
simian, murine, and bovine sequences is shown in
See Table 3. Figure 4.
Table 3 OSM protein sequences
Species Accession no. Source Type Size (aa) References
Human 129168 U937 cells Complete 252 Malik et al., 1989
2935614 Complete 252 Unpublished
246727 Kaposi’s sarcoma cells Partial, N-terminal 20 Nair et al., 1992
Simian Not deposited CV1 cells Partial, mature 196 Bruce et al., 1992b
Mouse 1709466 BF-EGFR/EPORH cells Complete 263 Yoshimura et al., 1996
Bovine 1709463 Complete 245 Malik et al., 1995
Figure 4 Comparison of human, simian, murine, and bovine OSM sequences.
Undetermined residues in the simian sequence are indicated (.). The predicted (cid:11)
helical and turn domains are shown (Kitchen et al., 1998). The N- and C-terminal
cleavage sites are indicated with an arrow and the signal peptide is indicated.
Oncostatin M 591
Description of proteins Human, simian, murine, and bovine OSM contain
four conserved cysteine residues. The human and
simian sequences contain an additional cysteine in
The proposed structures of human, bovine, and
helix B that is absent from the murine and bovine
murineOSMarecomparedinTable4.TheOSMgene
sequences. Mutational studies have shown that a
encodes a pre-pro OSM precursor which is processed
disulfide bond between the second and fifth cysteine
posttranslationallyatboththeN-andC-termini.The
residuesofhumanOSMisrequiredforactivity,while
N-terminal hydrophobic signal sequence, (cid:24) 23–25
a bond between the first and fourth cysteine residues
residues, is removed during the secretory process. An
is not (Kallestad et al., 1991). The mature, natural
additional cleavage occurs after a pair of basic resi-
forms of hOSM and bOSM migrate in SDS-PAGE
dues in the C-terminal domain, removing 31–57 resi-
with an apparent molecular weight of 28kDa under
dues, depending on the species, yielding the mature
both reducing and nonreducing conditions (Zarling
formofthesecretedprotein(Linsleyetal.,1990).The
et al., 1986; Malik et al., 1992). This agrees with the
196 amino acid mature human OSM is the predomi-
results from size-exclusion chromatography, which
nant form isolated from PMA-treated U937 cells and
indicate that the active form of the molecule is a
from CHO cells transfected with the hOSM cDNA.
monomer.
The227aminoacidformofOSM(pro-hOSM)has
been isolated from COS cells transfected with the
hOSMcDNA. Thispro-OSMform isasactiveasthe
Discussion of crystal structure
196-residue mature hOSM in competition binding
assays, but is 5-fold to 60-fold less active in growth
inhibition assays on A375 cells (Linsley et al., 1990). Although a crystal structure for OSM has not yet
While transfection of the full-length human OSM been described, the structures for related proteins,
cDNA in COS cells appears to produce primarily the including LIF, G-CSF, and growth hormone (GH)
active,matureform,similarstudieswithmurineOSM have been determined (Betzel et al., 1993; Robinson
cDNA have resulted in only inactive forms of the et al., 1994). Using the structural similarities between
molecule(Yoshimuraetal.,1996).Thismaybedueto these proteins and OSM and NMR structural data
improper cleavage of the C-terminus of murine OSM obtained from OSM, a homology model of OSM has
in these cells. Although the 227 amino acid pro- been derived (Hoffman et al., 1996; Kitchen et al.,
hOSM has not yet been isolated from a natural 1998). This model demonstrates that OSM adopts
source, tissue-specific processing could result in two a four (cid:11)-helical bundle structure similar to that
forms of hOSM having distinct biological functions determinedforothercytokines,ashadbeenpredicted
in vivo. High and low molecular weight forms of rat earlier (Rose and Bruce, 1991). The proposed struc-
OSM have been detected in developing testis (de ture for OSM is supported by mutational analysis,
Miguel et al., 1997). which demonstrated that discontinuous regions,
Table 4 OSM protein structure
Properties Human Simian Murine Bovine
OSM (aa) OSM (aa) OSM (aa) OSM (aa)
Precursor 252 nd 263 245
Signal peptide 25 nd 23 23
Pro-protein 227 nd 240 222
Excised C-terminal peptide 31 nd 57 39
Mature protein 196 196 183 183
Cysteine residues 5 5 4 4
Disulfide linkages 2 2 2 2
N-linked glycosylation sites 3 3 3 1
Identity to human OSM 100% 93% 48% 58%
nd,notdetermined.
592 A. Gregory Bruce and Timothy M. Rose
primarilyintheexceptionallyamphipathicC-terminal CELLULAR SOURCES AND
helix, are involved in receptor binding (Kallestad
TISSUE EXPRESSION
et al., 1991).
Cellular sources that produce
Important homologies
Human OSM has been purified from supernatants of
U937 histiocytic lymphoma cells induced to differ-
An alignment of the amino acid sequences of OSM
entiate with phorbol 12-myristate 13-acetate (PMA)
from derived from four different species is shown in
(Zarling et al., 1986) and T-lymphocytes treated with
Figure 4. Significant amino acid similarity is detected
phytohemagglutinin or mAb 9.3 (anti-human CD28)
throughout the coding regions and obvious con-
(Brown et al., 1987). In addition, using monoclonal
served sequence motifs are observed. The amino
antibodies, human OSM has been detected in cell
acid sequence of human OSM is 93% identical to
culturesderivedfromAIDS-relatedKaposi’ssarcoma
simian OSM, 58% identical to bovine OSM, and
(Nair et al., 1992) and retrovirus-infected CD4(cid:135) T
48% identical to murine OSM (Table 4). Murine
cells (Radka et al., 1993). OSM is also produced by
OSM is 42% identical to bovine OSM. The most
human synovial tissue macrophages (Okamoto et al.,
important conserved motif is found within the C-
1997).MurineOSMisexpressedatsignificantlevelsin
terminal helix and contains the sequence pattern
bonemarrowinmaturemice(Yoshimuraetal.,1996)
‘GYHRFM’. This region is believed to be a major
and has been detected in the gonads of developing
binding site with the OSM receptor. OSM shares
embryos(Hara et al., 1998). OSMis highly expressed
sequence homology and structural similarities with
inthelatefetalandearlyneonatalrattestis,aswellas
LIF and other members of the IL-6 family of
inthematuringandadulttestis(deMigueletal.,1997).
cytokines, including IL-6, G-CSF, CNTF, IL-11,
andCT-1 (RoseandBruce, 1991;Bazan,1991;Bruce
et al., 1996). Eliciting and inhibitory stimuli,
including exogenous and
Posttranslational modifications endogenous modulators
As described above, the OSM gene encodes a pre- EarlystudiesinU937histocyticleukemiacellsshowed
pro OSM precursor which is processed posttransla- that phorbol esters (PMA) induced the general
tionally atboththeN- andC-termini. AnN-terminal expression of human OSM. Murine OSM has been
hydrophobic signal sequence is removed during shown to be an immediate early gene induced by
the secretion process and a C-terminal peptide is multiple cytokines, including IL-2, IL-3, and EPO
cleavedatatrypsin-likerecognitionsequence(RSRR) (Yoshimura et al., 1996).
(Table 4; Figure 4). OSM is a glycoprotein which is There are no known exogenous or endogenous
modified by N-linked and, possibly, O-linked glyco- modulators of OSM.
sylation (Linsley et al., 1990). The human, bovine,
andsimiansequencescontainaconservedaminoacid
RECEPTOR UTILIZATION
site which may be N-linked glycosylated. A second
potential N-linked glycosylation site is conserved in
the human and simian sequences, but is absent from High- and low-affinity receptors for OSM have been
the bovine sequence. There is evidence from hOSM detectedonawidevarietyofcelltypes(Linsleyetal.,
(natural-, CHO-, and COS-derived) that this second 1989;Hornetal.,1990).Thelow-affinityreceptorfor
siteisnotused(Linsleyetal.,1990;Maliketal.,1989). OSM has been identified as gp130, a molecule pre-
There are three potential glycosylation sites in the viously shown to be the signaling subunit of the IL-6
murine OSM but none of these sites is positionally receptor complex (Hibi et al., 1996). Structural and
conserved in the other sequences. Recombinant functionalcharacterizationofgp130hasshownthatit
human OSM expressed in bacteria is fully active belongs to a family of related cytokine receptors
in vitro, indicating that glycosylation is not required (Bazan, 1991). Receptor binding in this family is
for biological activity. Human, simian, bovine, and characterized by low-affinity binding to an ‘alpha’
murine OSM each contain two conserved intramole- receptor which is converted to high affinity in the
cular disulfide bonds, one of which is required for presence of an additional related ‘beta’ receptor
activity (Kallestad et al., 1991). subunit/subunits. Because gp130 is the low-affinity
Oncostatin M 593
receptor for OSM, it is herein designated as OSMR(cid:11) and maintenance of murine ES cells in an undiffer-
(gp130). Two different high-affinity heterodimeric entiated state.
receptor complexes have been identified in humans;
an OSM-specific receptor complex composed of
OSMR(cid:11) (gp130) and a high-affinity converting IN VIVO BIOLOGICAL
receptorsubunit,OSM‘beta’receptor(OSMR(cid:12)),and ACTIVITIES OF LIGANDS IN
a receptor complex shared with LIF composed of
ANIMAL MODELS
OSMR(cid:11) (gp130) and the LIF ‘alpha’ receptor
(LIFR(cid:11)). This differs from the binding seen in the
Normal physiological roles
mouse, where murine OSM only binds the murine
OSM-specific receptor complex and not the LIF
receptorcomplex.Itshouldbepointedoutthathuman The normal physiological roles of OSM are not yet
OSM,usedinearlyinvitroandinvivoexperimentsin known. There is evidence in mice that mOSM may
mice, binds only the murine LIF receptor complex play a role in germ-cell development as a stage- and
and not the murine OSM receptor complex and thus sex-specific autocrine growth factor for Sertoli cells
mimics the activity of LIF in mice. (Hara et al., 1998).
Species differences
IN VITRO ACTIVITIES
In vitro findings The differences between the biological roles of
OSM in different species are not yet understood.
The findings that human OSM acts through both the
While a number of biological activities have been
human OSM-specific receptor and the shared LIF/
defined for OSM from in vitro studies, its primary
OSM receptor while murine OSM acts through the
biological role is still not clearly defined. Current
murine OSM-specific receptor but not the murine
evidence suggests that OSM plays a role in hemato-
LIF receptor, suggests that there will be signifi-
poiesis, neuropoiesis, bone growth, and regulation of
cant differences between mouse and human OSM
immune responses (Table 5).
bioactivities.
Regulatory molecules: Inhibitors
Transgenic overexpression
and enhancers
Bovine OSM has been overexpressed in transgenic
Soluble forms of OSMR(cid:11) (gp130) which bind OSM mice using various tissue-specific promoters. While a
at low affinity act as antagonists (Montero-Julian wide variety of developmental abnormalities were
et al., 1997). detected, the results are not interpretable since it is
likelythatbovineOSM,likehumanOSM,mimicsthe
effects of murine LIF in the transgenic mice rather
Bioassays used
than the effects of murine OSM. It will be necessary
to use murine OSM transgenes to determine the bio-
Human OSM bioactivity has been determined by a logicaleffectsofOSMinmice.However,thiswillstill
numberofbioassays(Table5)includinggrowthinhib- not completely determine the function of OSM in
ition of human melanoma A375 cells (Malik et al., humans and other species in which OSM can signal
1992), differentiation of human TH-1 (Liu et al., throughboththeOSM-specificreceptorandtheLIF/
1994)ormurinemyeloidleukemiaM1cells(Roseand OSM shared receptor.
Bruce, 1991) and maintenance of murine ES cells in
anundifferentiatedstate(Roseetal.,1993).Itshould
Interactions with cytokine network
be noted that the assays on mouse cells are based on
interaction of human OSM with the mouse LIF
receptor, not the OSM receptor. A hOSM-specific OSM induces expression of IL-6 and the IL-6 recep-
ELISA is commercially available. tor in certain cell types. Several studies have
Murine OSM bioactivity has been determined by demonstrated a synergy with TGF(cid:12). In mice, OSM
growth inhibition of murine myeloid leukemia M1 or is an immediate early gene induced by IL-2, IL-3,
NIH 3T3 cells, support of murine DA-1 cell growth and EPO.
594 A. Gregory Bruce and Timothy M. Rose
Table 5 In vitro properties of OSMa
Property Species Cell type References
(cid:11) -Antichymotrypsin induction Human HepG2 hepatoma Richards et al., 1992
1
Human Astrocytes Kordula et al., 1998
Human Lung epithelial Cichy et al., 1995
(cid:11) -Antitrypsin induction Human A549 epithelial Boutten et al., 1998
1
(cid:11) -Proteinase inhibitor induction Human A549 epithelial Sallenave et al., 1997
1
Human HTB58 lung epithelial Cichy et al., 1997a
Cell survival enhancement Mouse Primordial germ Hara et al., 1998
Differentiation induction Human U937 leukemia Bruce et al., 1992a
Human Breast cancer Douglas et al., 1998
EGR-1, c-jun, c-myc induction Human Fibroblasts Liu et al., 1992
Endothelin 1 induction Human HUVEC endothelial Saijonmaa et al., 1998
G-CSFb and GM-CSFc induction Human HEC endothelial Brown et al., 1993
Growth inhibition Human Various tumor Horn et al., 1990
Human Melanoma Brown et al., 1987;
Gibbs et al., 1998
Human Endothelial Takashima and
Klagsbrun, 1996
Haptoglobin induction Human HepG2 hepatoma Richards et al., 1992
IL-6 induction Human Lung fibroblast Richards and Agro,
1994
Human HEC endothelial Brown et al., 1991
LDLc modification Human U937 leukemia Maziere et al., 1994
LDL receptor induction Human HepG2 hepatoma Grove et al., 1991
Matrix metalloproteinase 1 induction Human Dermal fibroblasts Korzus et al., 1997
P21 kinase inhibitor induction Human MG63 osteosarcoma Bellido et al., 1998
p42MAPK/ERK-2 kinase induction Human Kaposi’s sarcoma Amaral et al., 1993;
Faris et al., 1996
p62yes tyrosine kinase induction Human HEC endothelial Schieven et al., 1992
Plasminogen activator induction Human Brown et al., 1990
Human Synovial fibroblasts Hamilton et al., 1991
Human HepG2 hepatoma Okada et al., 1996
Polykaryon formation Human Bone marrow Heymann et al., 1998
Proliferation induction Human Kaposi’s sarcoma Miles et al., 1992;
Nair et al., 1992;
Cai et al., 1994
Human Various normal Horn et al., 1990
P-selectin induction Human Endothelial Yao et al., 1996
Soluble IL-6 receptor induction Human HepG2 Cichy et al., 1997b
TIMP-1d induction Human Articular cartilage Nemoto et al., 1996
Human Synovial lining Gatsios et al., 1996
Mouse NIH 3T3 fibroblasts Richards et al., 1997
Human Fibroblasts Korzus et al., 1997