Vol. 147, No. 3, 1987
BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS
Pages 1219-1225
September 30, 1987
THE MEMBRANE-ANCHOR OF PARAMECIUM TEMPERATURE-SPECIFIC
SURFACE ANTIGENS IS A GLYCOSYLINOSITOL PHOSPHOLIPID
Yvonne
Capdeville,
M. L u c i a
and C n r i s t i a n e
Centre
Centre
Cardoso
de Gdn@tique
National
91190
Mol~culaire,
de la Recherche
Gif/Yvette,
+Molteno
de A l m e i d a , +
Deregnaucourt
Scientifique,
France
Institute,
Cambridge,
England
Received August 19, 1987
SUMMARY:
The temperature-specific G surface antigen of P a r a m e c i u m
p r i m a u r e l i a s t r a i n 156 was b i o s y n t h e t i c a l l y l a b e l e d Oy[~H3myrist-~c ~
~n
its membrane-bound form, Out not in its soluble form. It could be cleaved
by a phosphatidylinositol-specific phosphotipase C from Trypanosoma brucei
or from Bacillus cereus which released its soluble form with the unmasking
of a particular glycosidic i m m u n o d e t e r m i n a n t catted the crossreacting
determinant. The P a r a m e c i u m enzyme, capable of converting its membranebound form into the soluble one, was inhibited by a sulphydril reagent in
the same way as the trypanosomal t i p a s e . From t h i s evidence we propose t h a t
the Paramecium t e m p e r a t u r e - s p e c i f i c s u r f a c e a n t i g e n s are anchored i n the
plasma membrane via a glycophosphotipid,
and t h a t an endogenous
phosphotipase C may be i n v o l v e d i n the a n t i g e n i c v a r i a t i o n process.
® 1987
Academic Press, Inc.
The s u r f a c e o f Paramecium a u r e i i a ,
m a i n l y by a
a ciliated
protozoan,
is c o a t e d
s i n g l e s e t o f m o l e c u l e s , t h e s u r f a c e a n t i g e n s (SAgs). These
high molecular weight proteins (250 - 300 kDa) Belong to a multigene family
whose
expression
interatlelic
(2,
involves
mechanisms
3) exclusion,
and
of
their
mutual
intergenic
expression
is
(1) and
essentially
controlled by external factors, such as temperature (for a review, 4, 5).
A b b r e v i a t i o n s : SAg, surface a n t i g e n ; mSAg, membrane-bound surface a n t i g e n ;
sSAg, s o l u b l e s u r f a c e a n t i g e n ; CRG, c r o s s r e a c t i n g g l y c o p r o t e i n ;
VSG,
variant
surface
glycoprotein;
PIPLC, p h o s p h a t i d y l i n o s i t o l - s p e c i f i c
phospholipase C; CRD, c r o s s r e a c t i n g d e t e r m i n a n t .
+ C o r r e s p o n d e n c e a d d r e s s : Y. C a p d e v i l l e , C e n t r e de G@n@tique M o l @ e u l a i r e ,
Centre N a t i o n a l de l a Recherche S c i e n t i f i q u e , 91190 G i f / Y v e t t e , France.
0006-291X/87 $1.50
1219
Copyright © 1987 by Academic Press, Inc.
All rights of reproduction in any form reserved.
Vol. 147, No. 3, 1987
Paramecium
BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS
SAgs can be isolated either in a m e m b r a n e - b o u n d
form (mSAg)
which is amphipnilic or in a soluDle form (sSAg) which is hydrophilic (6).
The membrane-bound
form
(mSAg),
found in celts stably expressing a given
SAg can be converted to the soluble form (sSAg) by incubating paramecia in
ethanolic solution or in Triton X-IO0 (7). The conversion of mSAg to sSAg
is
accompanied
by
immunodeterminant
determinant)
release
of
a
particular
glycosidic
is located
in
the
COOH-terminal
glycopeptide
of
(for a review, 8). Together with sSAg molecules, there is
of a set
crossreacting
unmasking
crossreacting with the so-called CRD (for crossreacting
which
Trypanosoma VSGs
the
of 45-50
glycoproteins),
kDa
molecules,
which,
now
denoted
after reduetion~
CRGs
(for
crossreact with all
the sSAgs and also display the CRD (6, 7). This conversion is mediated by
an
enzyme
which
phenantrolin
can
(7),
be
in
inhibited
the
phosphatidyiinositol-specific
same
by
Zn 2+
and
fashion
as
Cd 2+,
but
not
Trypanosoma
by
o-
brucei
phospholipase C (PIPLC) (9) which solubilizes
the VSGs, cleaving their lipid anchor (lO, ll).
These features are similar to that found in surface proteins anchored in
the plasma m e m b r a n e
via a phosphatidylinositol
(for a review,
12, 15).
Therefore, in order to demonstrate that Paramecium surface antigens display
the same type of membrane anchor~ the strain 156 of Paramecium primaurelia,
expressing the temperature-specific
?H/myristic acid,and t h e
,.
G SAg, was biosynthetically labeled by
capability
o f PIPLC f r o m T. b r u c e i
(14-16) or
.
from B a c i l l u s
cereus (17) f o r c o n v e r t i n g t h e mSAg i n t o
sSAg was checked.
MATERIALS AND METHODS
Cellular
fractions
were prepared from strain
156 o f P_z_- p r i m a u r e l i a
e x p r e s s i n g t h e s u r f a c e a n t i g e n G (156G SAg) and the i d e n t i f i c a t i o n
of the
expressed SAg was p e r f o r m e d as d e s c r i b e d p r e v i o u s l y (2). C e l l u l a r e t h a n o l i c
extracts were o b t a i n e d by incubating cells (1 vol) in a salt ethanolic
solution (4 vol) (0.45W NaC1, 15~ ethanol, 5 mM phosphate Duffer, pH 7) for
45 min at 4°C (18). The detailed preparations of ciliary membranes have
been described in a previous paper (6). 156G SAg was purified by the method
of Preer (18), followed By ultrafittration on Sephadex G-200 superfine
(Pharmacia). Phcspholipase C from T. brucei (ILTat 1.25) was obtained by
soluuilization of VSG-depleted membranes in n-beryl glycoside~ followed by
chromatography on Affi-gel 501 (Bio-Rad)
(19). Phospholipase C, type lit,
from B_~.cereus, p-chloromercuripUenylsulfonic acid (pCMPSA), defatted BSA,
leupeptin and p h e n y l m e t h y l s u l f o n y l f l u o r i e e (PMSF) were purchased from
Sigma, 9,10-SH(n) myristic acid (55 Ci/mmol) and 9,10-~H(n) palmitic acid
(50 Ci/mmol) from Amersham.
Biosynthetic labeling with ~H]myristic acid: washed paramecia (2xlOS~ml)
were incubated at 27°CJin lOml Dryl's mineral solution(20) with[3H]
myristic acid-BSA complex or with ~H]palmitic acid-BSA complex (I0 mg BSA,
500 ~Ci) for 150 min. lO ml culture medium was then added and incubation
continued for another 150 min. Cells were harvested and washed, then they
were either lyzed in boiling 5~ SDS or submitted to ethanolic extraction
in the presence or in the absence of 1 mM pCMPSA. After SDS-PAGE on a 5-15~
acrylamide gradient gel, performed as described previously (6), destained
1220
Vol. 147, No. 3, 1987
B I O C H E M I C AAND
L
BIOPHYSICAL RESEARCH COMMUNICATIONS
gels were treated with Amplify (Amersham) for 30 min, dried and exposed to
Kodak X-Omat AR film at -70°C for I0 days.
Lipase treatment: Phospholipase digestions of 156G mSAg were performed on
fractions (ciliary membranes, 25 ~g; ethenolie cellular extracts, 40 pg;
purified SAg, 20 ~g) prepared in the presence of imM pCMPSA (which was then
removed by dialysis or by dilution in the case of ciliary membranes). The
digestions were carried out for 50 min at 30°C in the following conditions:
(a) in lO mM Tris-HC1, 150 mM NaC1 pH 7.4 (TBS) plus 0.5 mM dithiothreitol,
0.1% Triton X-114 and 0.01% sodium deoxycholate in the presence of (1
H1/ml) a f f i n i t y - p u r i f i e d phospholipase C of T. brueei; (b) in TBS plus
0.06% Triton X-114 in the presence of phospholipase C (lO units/ml) from B__~.
cereus. The conversion of mSAg to sSAg was monitored by the immunological
detection of the CRD exposure (7). Anti-CRD antibody was prepared by
immunizing rabbits with VSG followed by affinity purification as describes
in (lO). A n t i s e r u m 2555 raised against purified 156G sSAg was used in
immunoblotting experiments as previously described (6).
Protease inhibitors: 0.28mM PMSF, O.OlmM leupeptin and lmM EDTA were used
during the course of extractions and sample preparations.
RESULTS
Inhibition of endogenous conversion by pCMPSA:
Incubation of paramecia in
ethanolic solution led to the soluOilization of SAg along with CRGs and the
appearance of anti-CRD binding epitopes in SAg and also in CRGs (Fig. l,
lane I). However, when the same incubation was performed in the presence of
1 mM pCMPSA the anti-CRD binding was no longer detectable either on SAg or
on CRGs (Fig. 1B, lane 2), and the CRG determinant, common to sSAgs, which
is specifically
recognized by antiserum 2355
(7)
was not r e v e a l e d ( Fig .
1A, lane 2). This i n d i c a t e s t h a t Paramecium has an endogenous enzyme, a b l e
to disclose the CRD and another determinant common to sSAgs and CRGs, which
ean be inhibited Oy the thiol reagent pCMPSA in a manner analogous to the
trypanosomal PIPLC
(21).
Fatty acxlation o f mSAq:
Paramecia were biosynthetically labeled w i t h [ 3 ~
m y r i s t i e acid as described in M a t e r i a l s and Methods. The SAg appeared
strongly labeled at 300 min while other polypeptides were already labeled
at 150 min of incubation (Fig. 2B, lanes 1 and 2). When a sample of cells
labeled for 500 min was extracted in ethanol under the usual eonditions,
the label associated with SAg disappeared (lane 3). However,
when this
extraction was performed in the presence of 1 mM pCMPSA the SAg remained
labeled ( l a n e 4), indicating t h a t ~ H I m y r i s t i c acid label was associated
w i t h the membrane-bound form of SAg. The o t h e r bands which remained l a b e l e d
under both c o n d i t i o n s of e t h a n o l i c e x t r a c t i o n might correspond to p r o t e i n s
directly
acylated
(22). Our a t t e m p t s to i n c o r p o r a t e 15HI p a l m i t i c acid unSer
the same c o n d i t i o n s d i d not r e s u l t i n l a b e l e d SAg.
Treatment of m S A q b y f .
Orucei PIPLC: Ciliary membranes, ethanolic cellular
extracts and purified 156G SAg were prepared in the presence of pCMPSA 9 in
order to inhibit endogenous conversion,
excess inhibitor.
1221
and further dialysed to r e m o v e
Vol. 147, No. 3, 1 9 8 7
BIOCHEMICAL A N D BIOPHYSICAL RESEARCH C O M M U N I C A T I O N S
A
A
B
1
1
1
2
3
B
4
1
2
3
4
SAg..~
SAg .l=,,-
c.G l
Q
®
Fig. i. Inhibition of conversion b ~ pCMPSA: 156G ethanolic cellular
extracts prepared without (lane i) or with i mR pCMPSA (lane 2) were
reduced and analyzed Dy SDS-PAGE and immunoOlotting. (A) immunoblot
obtained with an anti-156G serum (AS 2355). (B) replica immunoDlot p~obed
with anti-CRD. SAg: 156G SAg; CRG: crossreacting glycoproteins.
Fig. 2. Fatty ~ o f
mSAq: (A) and (B): Paramecia (2xlO 5 cells) were
la-bel~ with ~H] myristic acid as described in Materials and Methods for
300 min. After 150 min of labeling, an aliquot of 5xlO 4 cell equivalents
was h a r v e s t e d and l y s e d i n b o i l i n g
5W 5DS. At t h e end o f t h e l a b e l i n g
experiment (500 min)~ the remaining cells were split into three aliquots of
5xlO4 cells. One was boiled in 5~ SD5 and the ether two were extracted with
ethanol in the presence or in the absence of I mM pCMPSA. The four samples
were submitted to SDS-PAGE: the Coomassie-mlue stained gel is shown in A
and the corresponding fluorogramm in B. Lanes 1 and 2: whole cells lysed in
SDS after 150 and 300 min of tsbeling~ respectively. Lanes 3 and 4:
e t h a n e l i c e x t r a c t s o f c e l l s l a b e l e d f o r 300 min and p r e p a r e d i n the absence
or presence o f 1 mM pCMPSA, r e s p e c t i v e l y . The h i g h m o l e c u l a r w e i g h t bands
found i n e t h a n o l i c e x t r a c t s c o r r e s p o n d to SAg m o l e c u l e s , as SAg i s the o n l y
high molecular weight protein extracted
with ethanol (6). Note that a
l e s s e r amount o f SAg m o l e c u l e s i s e x t r a c t e d w i t h e t h a n o l i n the presence o f
pCHSA.
The lipase digestion could not De assessed by phase separation using Triton
X-114
(23), as mSAg
Therefore~
molecules
were not recovered
this was assessed by checking
in the detergent
phase.
the Binding of purified anti-CRD
to SAg and to CRGs. The t r e a t m e n t by T. b r u c e i P I P L C (Fig. 3, lanes 4, 5, 7
and 9) led to the a p p e a r a n c e
of a n t i - C R D e p i t o p e s in SAg and also in C R G s
(Fig. 3B), and to the r e c o g n i t i o n
of CRGs Dy an a n t i - 1 5 6 G s e r u m (AS 2355)
(Fig. 3A). The B. c e r e u s P I P L C c o u l d also d i s c l o s e the CRD and lead to the
CRG recognition by the antiserum
2355 (data net shown).
DISCUSSION
The r e s u l t s
fatty
described
acylated
in
in their
this
paper
demonstrate
membrane-bound
lost after conversion of mSAg to sSAg,
s S A g can be p e r f o r m e d
that
Paramecium
form 9 since incorporated
SAgs
label
are
is
and that this conversion of mSAg to
by I. b r u c e i or B__~.c e r e u s PIPLC. S i n c e the T. b r u c e i
1222
Vol. 147, No. 3, 1987
BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS
2
3
-
4
+
_
5
+
6
-
7
q-
8
_
9
+
A
SAg~
c.GI
Viq. 3. Treatment of mSAq b ~ T. Orueei PIPLC: Different fractions
containing mSAg'were prepared and incubated with T. Drueei PIPLC, as
indicated in Materials and Methods. Then, samples were reduced prior to
analysis by 5DS-PAGE and immunoOlotting. (A) immunoDlot oOtained with an
anti-156G serum (AS 2355); (B) replies immunoblot prooed with anti-CRD.
Lane 1: ethsnolie cellular extract prepared in the absence of pCMPSA and
used as control; lanes 2-9: different fractions (lanes 2-5: ciliary
membranes, lanes 6 and 7: ethanolie cellular extract, lanes 8 and 9:
purified 156G SAg) prepared in the presence of pCMPSA and ineuoated without
(-) or with (+) T. Urueei PIPLC.
PIPLC has b e e n f o u n d
substrate
(14-16)
to
selectively
we a r e
led
to conclude
a n c h o r e d in t h e p l a s m a m e m b r a n e
secondly,
that in Paramecium
a phospholipase
C similar
recognize
features
that,
firstly,
by a g l y e o s y l i n o s i t o l
of
glycolipid
t h e SAgs a r e
phospholipid,
end
the endogenous conversion can be performed by
to that of T. b r u c e i ,
since
both enzymes
are
inhibited by the same reagents. Furthermore the new facts described in this
paper point
to the possibility
post-translational
that P a r a m e c i u m
modification,
as that
1223
displays
found
the same
in T. b r u e e i
type
VSGs
of
(24).
Vol. 147, No. 3, 1987
B I O C H E M I C AAND
L
BIOPHYSICAL RESEARCH COMMUNICATIONS
Finally, it is tempting to assign a role to the phosphatidylinositol anchor
of SAgs in combination with endogenous PIPLC in the antigenic variation
process, as antigenic variation in P a r a m e c i u m
is triggered by external
factors and as SAg itself has been previously shown to be directly involved
i n this phenomenon
As for the CRGs,
immunological
(25).
found in ethanolie
means
end
only
cellular
following
extracts,
reduction,
detectable
their
binding
by
to
a n t i b o d i e s a g a i n s t sSAgs or a g a i n s t CRD r e q u i r e s the a c t i o n o f endogenous
or exogenous PIPLC to unmask the corresponding e p i t o p e s . Thus, the q u e s t i o n
arises whether they derive from SAg by proteolytie events occurring before
or a f t e r t h e a c t i o n of t h e PIPLC, o r whether they c o r r e s p o n d to a s e t of
other m e m b r a n e proteins that are also bound to the plasma m e m b r a n e by a
glycolipid anchor. Results demonstrating
that they correspond to other
membrane proteins are reported elsewhere (26).
ACKNOWLEDGEMENTS
We thank C. Bordier very much for fruitful discussions. This work was
supported in part by the C.N.R.S. (grant 900264), and by the Ligue
Nationale Fran£aise con,re le Cancer. C.D. was supported by a fellowship
from l'Association pour la Recherche sur le Cancer. M.L.C. de Almeida
received support from St John'S College, Cambridge.
REFERENCES
I_~. Beale, G.H. (1952) Genetics 37, 62-74.
2 , Capdeville, Y. (1971) Hal. Gen. Gen. 112, 306-316.
3 . Capdeville, Y., Vierny, C. and Keller, A.M. (19783 Mol. Gen. Gen. 161,
23-29.
4__t.Beale , G.H. (1954) in: The genetics of P a r a m e c i u m aurelia (5all, G. ed)
pp 77-123, University Press, Cambridge.
5 . Sonneborn, T.M. (1974) in: Handbook of genetics (King, R.C. ed) vol. 2,
pp 469-594~ Plenum Press, New-York, London.
6 . Capdeville, Y., Deregnaucourt, C. and Keller, A.H. (1985) Experim. Cell
Res. 161, 495-508.
7 . Capdeville, Y., Baltz, T., Deregnsucourt, C. and Keller, A.M. (19863
Experim. Cell Res. 167, 75-86.
8/_. Turner t M.3., Cardoso de Almeids, M.L., Gurnett, A.M., Raper, J. and
Ward, a. (1989) Curr. Top. Microbial. Immunol. 117, 23-55.
9___~.Cardoso de Almeida, M.L., Allan, L.N. and Turner, N.J. (1984) a. Protoz.
31, 55-60.
i0___t.
_ Csrdoso de Almeida, M.L. and Turner, M.J. (1983) Nature 302, 349-352.
Ii • Ferguson, M.A.J., Haldar, K. and Cross, G.A.M. (19853 5. Biol. Chem.
260, 4963-4968.
12. Low, H.G., Ferguson, M.A.J., Futerman, A.H. and 5ilman, I. (1986)TIBS
ii, 212-215.
!3. Cross, G.A.M. (19873 Cell 48, 179-181.
!4 . BSlow, R. and Overs,h, P. (1986) 5. Biol. Chem. 2619 11918-11923.
15 . Hereld, D., Krakow, J.L., Bangs, 5.D., Hart, G.W. and Englund, P.T.
(1986) 5. Biol. Chem. 261, 13813-13819.
1224
Vol. 147, No. 3, 1987
BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS
16 . Fox, 3.A., Duszenko, M., Ferguson, M.A.3., Low, M.G. and Cross, G.A.H.
(1986) J. B i o l . Chem. 261, 15767-15771.
17 . Ikezawa, I . and Taguchi, R. (1981) in Meth. in Enzym. v o l . 71, pp.
751-741.
18. P r e e r , 3.R., J r . (1959) J. lmmunol. 83, 579-584.
!9~ Ward, J., Cardoso de Almeida, M.L., Turner, M.3., Etges, R. and
B o r d i e r , C.(1897) Mot. Bioohem. P a r a s i t o l . 23, 1-7.
20___~.D r y l , S. (1959) J. P r o t o z o o l . 6 ( s u p p l . ) , 25.
21. B51ow, R. and Overath, P. (1985) FEBS L e t t . 187, 105-110.
22__z. Olson, E.N., Towler, D.A. and G l a s e r , L. (1985) 3. B i o l . Chem. 260,
3784-5790.
23. B o r d i e r , C. (1981) 3. B i o l . Chem. 256, 1604-1607.
24. Bangs, i.D., Andrews, N.W., H a r t , G.W. and Englund, P.T. (1986) 3. C e l l
Biol. I03, 255-263.
25. Capdeville, Y. (1979) J. Cell Physiol. 99, 383-393.
26. Deregnaueourt, C., Keller, A.M. and Capdeville, Y. (1987) submitted to
Biochem. J.
1225