1 ns into a critical cysteine in each of these
saposins.
2 of resident lipid transfer proteins, namely
saposins.
3 tion site are strictly conserved in all four
saposins.
4 t sphingolipid-activating proteins (SAPs) or
saposins.
5 ich ultimately caused depletion of lysosomal
saposins.
6 me cases, by lipid transfer proteins such as
saposins.
7 Individual
saposin A (A-/-) and saposin B (B-/-)-deficient mice sho
8 Saposin A (SapA) lipoprotein discs, also known as picodi
9 the nonsignal NH2-terminal peptide preceding
saposin A (termed Nter) was usually removed prior to sap
10 d saposins C and A, wild-type saposin C, and
saposin A [Y30A], poorly with saposin C [A31Y], and not
11 In the absence of lipid,
saposin A adopts a closed monomeric apo conformation typ
12 osed of human sphingolipid activator protein
saposin A and a small number of phospholipids, to displa
13 Saposin A and B proteins were undetectable in AB-/- mice
14 By site-directed mutagenesis of
saposin A and C, their membrane topological structures w
15 nted using picodiscs (complexes comprised of
saposin A and lipids, PDs), to screen mixtures of glycol
16 A (termed Nter) was usually removed prior to
saposin A cleavage.
17 Saposin A contains an additional glycosylation site and
18 hat, in addition to GALC deficiency, genetic
saposin A deficiency could also cause chronic GLD.
19 Genetic
saposin A deficiency might be anticipated among human pa
20 genic activity whereas reduced and alkylated
saposin A did.
21 an amino acid substitution (C106F) into the
saposin A domain by the Cre/loxP system which eliminated
22 Wild-type
saposin A had no neuritogenic activity whereas reduced a
23 Saposin A has roles in sphingolipid catabolism and trans
24 The structure reveals two chains of
saposin A in an open conformation encapsulating 40 inter
25 tein, we determined the crystal structure of
saposin A in the presence of detergent to 1.9 A resoluti
26 Thus,
saposin A is indispensable for in vivo degradation of ga
27 Saposin A lipoprotein discs exhibit limited selectivity
28 However, no specific
saposin A or D deficiency is known.
29 logy of incorporating membrane proteins into
saposin A picodiscs for MS footprinting.
30 on of saposin C, and the analogous region of
saposin A showed that more "saposin C-like" molecules ha
31 ic placement of amino acids, and that Y30 of
saposin A significantly alters local conformation in thi
32 Introduction of the conserved
saposin A Tyr 30 (Y30) into saposin C at the analogous p
33 through a tetrasaposin, A-B-C-D, from which
saposin A was then removed.
34 Nondenatured
saposin A with an introduced A30 acquired substantial ne
35 The phenotypic features of
saposin A(-/-) mice are qualitatively identical but mild
36 Saposin A(-/-) mice developed slowly progressive hind le
37 When
saposin A(-/-) mice were subcutaneously implanted with t
38 During intercrossing of
saposin A(-/-) mice, we observed that affected females t
39 ntly down-regulated in the brain of pregnant
saposin A(-/-) mice.
40 s and microglia in the demyelinating area of
saposin A(-/-) mice.
41 chronic form of the disease by inactivating
saposin A, the essential activator of galactosylceramida
42 Those with more "
saposin A-like" spectra did not.
43 osin C [A31Y], and not at all with wild-type
saposin A.
44 with amino acids in the analogous region of
saposin A.
45 These findings indicate that combined
saposins A and B deficiencies attenuated GalCer-beta-gal
46 created by knock-in point mutations into the
saposins A and B domains on the prosaposin locus.
47 n insight into the interrelated functions of
saposins A and B, combined saposin AB-deficient mice (AB
48 iencies of saposins C and D and decreases in
saposins A and B.
49 Saposins A and C were produced in Escherichia coli to co
50 elices at the amino- and carboxyl termini of
saposins A and C were shown to insert into the lipid bil
51 n models are proposed for the membrane-bound
saposins A and C.
52 In comparison, the middle region of
saposins A or C were either embedded in the bilayer or s
53 In C-/- mice, prosaposin and
saposins A, B and D proteins were present at near wild-t
54 Saposins A, B, C and D are derived from a common precurs
55 Sphingolipid activator proteins (
saposins A, B, C and D) are small homologous glycoprotei
56 otein that encodes four glycoproteins, named
saposins A, B, C and D.
57 precursor of four activator proteins, termed
saposins A, B, C, and D, that are required for much of g
58 Prosaposin, the precursor of
saposins A, B, C, and D, was recently identified as a ne
59 Prosaposin, the precursor of
saposins A, B, C, and D, was recently reported to be a n
60 zygotes (B-/-) mice, whereas prosaposin, and
saposins A, C and D were at normal levels.
61 Saposins (
A, B, C and D) are approximately 80 amino acid
62 Saposins (
A, B, C, and D) are small sphingolipid activat
63 Based on the
saposin-
A (SapA) scaffold protein, we demonstrate the su
64 ated functions of saposins A and B, combined
saposin AB-deficient mice (AB-/-) were created by knock-
65 Here we show that
saposins,
although not required for the autoreactive rec
66 We propose that MTP acts upstream of the
saposins and functions as an ER chaperone by loading end
67 res are closely related, suggesting that all
saposins and saposin-like domains share a common topolog
68 Total deficiency of all
saposins and specific deficiency of saposin B or C are k
69 The oligosaccharides on
saposins are not required for in vitro activation functi
70 Saposins are small, heat-stable glycoprotein activators
71 The
saposins are small, membrane-active proteins that exist
72 r proteins SAP-A, -B, -C and -D (also called
saposins)
are generated by proteolytic processing from a
73 Individual saposin A (A-/-) and
saposin B (B-/-)-deficient mice show unique phenotypes c
74 Saposin B (Sap B) is an essential activator protein for
75 Recently, native
saposin B (sapB) has been shown to bind CoQ10 and subseq
76 posins containing various length segments of
saposin B and C localized the neurotrophic and acid beta
77 Patients with kidney disease lacked
saposin B and showed new components in two patterns: the
78 Using
saposin B as a unreactive backbone, chimeric saposins co
79 We found that
saposin B bound to neutral glycosphingolipids and gangli
80 Saposin B could also mediate lipid binding to soluble CD
81 Blocking sulfatide degradation from the
saposin B deficiency diminished galactosylceramide accum
82 Saposin B derives from the multi-functional precursor, p
83 ng and compressing the central cavity of the
saposin B dimer, may play a key role in facilitating lip
84 These findings delineate the roles of
saposin B for the in vivo degradation of several GSLs an
85 ting a compensation in LacCer degradation by
saposin B for the saposin C deficiency.
86 We found that
saposin B forms soluble saposin protein-lipid complexes
87 wed few components other than two ubiquitous
saposin B glycoisoforms.
88 e of SDS is very similar to a monomer in the
saposin B homodimer structure.
89 of B-/- mice supporting the in vivo role of
saposin B in the degradation of these lipids.
90 ore assays we demonstrated that lipid-loaded
saposin B increases the off-rate of lipids bound to CD1d
91 Saposin B is a water soluble alpha-helical protein which
92 The X-ray structure of
saposin B is homodimeric.
93 gher than that of lysosomes, suggesting that
saposin B may facilitate lipid binding to CD1d molecules
94 Because
saposin B must bind lipids directly to function, we foun
95 y of all saposins and specific deficiency of
saposin B or C are known among human patients.
96 Mutations in
saposin B present in humans with phenotypes resembling m
97 No
saposin B protein was detected in the homozygotes (B-/-)
98 be absolutely essential, but the absence of
saposin B resulted in the lowest recognition of alpha-ga
99 Saposin B was also the most efficient in mediating alpha
100 were added to the prosaposin-negative cells,
saposin B was the most efficient in restoring CD1d recog
101 To gain insight into
saposin B's physiological functions, a specific deficien
102 lex formation between glycosphingolipids and
saposin B, a separate activator protein with broad speci
103 Similar to
saposin B, NPC2 dimers were able to load isoglobotrihexo
104 ort (5 ns) molecular dynamics simulations of
saposin B, starting from both the AB and CD conformation
105 The optimal pH for
saposin B-mediated lipid binding to CD1d, pH 6, is highe
106 Three of these
saposins (
B, C, and D) share common structural features
107 d by creating mice with selective absence of
saposin C (C-/-) using a knock-in point mutation (cystei
108 Saposin C (Sap C) is a small glycoprotein required for h
109 The interaction of
Saposin C (Sap C) with negatively charged phospholipids
110 ween GCase and its known facilitator protein
saposin C (SAPC).
111 Saposin C (Trp-free) induced additional activity and flu
112 saposin C, and saposin A [Y30A], poorly with
saposin C [A31Y], and not at all with wild-type saposin
113 Saposin C adopts the saposin-fold common to other member
114 CD spectral changes indicated
saposin C and acid beta-glucosidase interaction only in
115 The CD-/- mice with
saposin C and D combined deficiencies were produced by i
116 e curves demonstrated maximal enhancement by
saposin C and prosaptides at low nanomolar concentration
117 etectable in AB-/- mice, whereas prosaposin,
saposin C and saposin D were expressed near wild-type (W
118 of the conserved saposin A Tyr 30 (Y30) into
saposin C at the analogous position 31, a conserved Ala(
119 s the first representation of membrane bound
saposin C at the atomic level.
120 induces essential conformational changes for
saposin C binding and further enhancement of acid beta-g
121 Saposin C binds to membranes to activate lipid degradati
122 phospholipids or, particularly, phospholipid/
saposin C complexes by intrinsic fluorescence spectral s
123 ibodies directed against the NH2-terminus of
saposin C cross-reacted well with reduced and alkylated
124 The few patients with
saposin C deficiency develop a Gaucher disease-like cent
125 n in LacCer degradation by saposin B for the
saposin C deficiency.
126 the above homozygous mutant GCase mice into
Saposin C deficient (C*) mice.
127 t the in vivo effects of saposin C on GCase,
saposin C deficient mice (C-/-) were backcrossed to poin
128 the membrane-binding behavior of a mutant of
saposin C designed to decrease the negative charge of th
129 lized to a 12-amino acid sequence within the
saposin C domain and has been used to derive biologicall
130 ing the neurotrophic sequence located in the
saposin C domain.
131 Deficits in
saposin C enhancement of k(cat) were present in variant
132 Saposin C enhances GCase activity and protects GCase fro
133 In contrast,
saposin C facilitates CD1 lipid loading in a different w
134 hway, acid beta-glucosidase (GCase) requires
saposin C for optimal in vitro and in vivo hydrolysis of
135 These results support the view that
saposin C has multiple roles in glycosphingolipid (GSL)
136 In addition, the deficiency of
saposin C in CD-/- mice resulted in cellular decreases o
137 st, the previously reported NMR structure of
saposin C in the absence of SDS is compact and contains
138 henotype and underscored the in vivo role of
Saposin C in the modulation of Gaucher disease.
139 The structure of
saposin C in the presence of SDS is very similar to a mo
140 the three-dimensional solution structure of
saposin C in the presence of the detergent sodium dodecy
141 Conformational changes of
saposin C induced by phosphatidylserine interaction sugg
142 Since
saposin C is a lysosomal protein and pH gradients occur
143 Saposin C is a lysosomal protein needed for optimal GCas
144 Saposin C is a lysosomal, membrane-binding protein that
145 Saposin C is an essential co-factor for the hydrolysis o
146 These data indicate that
saposin C is required for GCase resistance to proteolyti
147 The absence of
saposin C led to moderate increases in GC and lactosylce
148 negatively charged electrostatic surface of
saposin C needs to be partially neutralized to trigger m
149 To test the in vivo effects of
saposin C on GCase, saposin C deficient mice (C-/-) were
150 re present at near wild-type levels, but the
saposin C protein was absent.
151 Across species, this
saposin C region has a high degree of identity and simil
152 udies show that the neuritogenic activity of
saposin C requires specific placement of amino acids, an
153 Loading
saposin C to human PS-/- fibroblasts resulted in an enha
154 We find that the binding of
saposin C to phospholipid vesicles is a pH-controlled re
155 proper orientation of the middle segment of
saposin C to the outside of the membrane surface is crit
156 nesis localized the activation properties of
saposin C to the region spanning residues 47-62.
157 of neurotrophic and activation properties of
saposin C to two different faces of the molecule and sug
158 se neurotrophic and activation properties of
saposin C was elucidated using recombinant or chemically
159 Of the four mature saposins, only
saposin C was found to increase sulfatide concentrations
160 The in vivo effects of
saposin C were examined by creating mice with selective
161 To get insights into
saposin C's function, we have determined its three-dimen
162 the lysosome could be switched on and off by
saposin C's reversible binding to membranes.
163 ults in impaired processing of prosaposin to
saposin C, a critical activator of the lysosomal enzyme
164 f the pure enzyme requires phospholipids and
saposin C, an 80 aa activator protein.
165 These results indicate a new property for
saposin C, an anti-proteolytic protective function towar
166 ed and alkylated saposins C and A, wild-type
saposin C, and saposin A [Y30A], poorly with saposin C [
167 A, the corresponding neuritogenic region of
saposin C, and the analogous region of saposin A showed
168 ies to the carboxyl- and NH2-terminal 50% of
saposin C, respectively.
169 n B in mediating prosaposin cleavage to form
saposin C, the lysosomal coactivator of GCase.
170 Without
saposin C, the mutant GCase activities in the resultant
171 logous region of saposin A showed that more "
saposin C-like" molecules had neuritogenic properties.
172 as sufficient to upregulate cathepsin B- and
saposin C-mediated activation of GCase.
173 mutant neurons is rescued by treatment with
saposin C.
174 ~50% compared with those in the presence of
Saposin C.
175 ed only from the lack of GCase activation by
saposin C.
176 is localized to amino acid residues 22-31 of
saposin C.
177 neurite outgrowth in vitro via sequences in
saposin C.
178 resented at acidic pH and in the presence of
saposin C.
179 Wild-type and mutant
saposins C and A from human and mouse were expressed in
180 CD spectra of wild-type and mutant
saposins C and A, the corresponding neuritogenic region
181 ross-reacted well with reduced and alkylated
saposins C and A, wild-type saposin C, and saposin A [Y3
182 paired prosaposin secretion, deficiencies of
saposins C and D and decreases in saposins A and B.
183 r T (iNKT) cells, it remains unclear whether
saposins can facilitate loading of endogenous iNKT cell
184 We found that lysosomal pSAP and its single-
saposin cognates mediated disintegration of tumor cell-d
185 saposin B as a unreactive backbone, chimeric
saposins containing various length segments of saposin B
186 using recombinant or chemically synthesized
saposin Cs from various regions of the molecule.
187 he complement of disulfide bonds in selected
saposin Cs.
188 variants in the intronic regions of the PSAP
saposin D domain (rs4747203 and rs885828) in sporadic Pa
189 tic evidence for the involvement of the PSAP
saposin D domain in Parkinson's disease.
190 g revealed three pathogenic mutations in the
saposin D domain of PSAP from three families with autoso
191 Saposin D loading had no effect.
192 In mice, a Psap
saposin D mutation caused progressive motor decline and
193 B-/- mice, whereas prosaposin, saposin C and
saposin D were expressed near wild-type (WT) levels.
194 In both humans and mice, prosaposin/
saposin deficiencies lead to severe neurological deficit
195 A mouse model of total
saposin deficiency closely mimics the human disease.
196 Saposins,
derived from a common precursor, prosaposin, a
197 embrane interactions and orientations of the
saposins determine the proximity of their activation and
198 Both contain a signal sequence followed by a
saposin domain and a GDSL-lipase domain.
199 In vitro,
saposins extracted monomeric lipids from membranes and f
200 Saposins facilitate this process, but the mechanisms use
201 transfer proteins, such as molecules of the
saposin family, facilitate extraction of lipids from bio
202 mprised of four alpha-helices that adopt the
saposin fold, characteristic of a protein family that bi
203 Saposin C adopts the
saposin-
fold common to other members of the family.
204 elical bundle of granulysin resembles other "
saposin folds" (such as NK-lysin).
205 ic reticulum is complementary to that of the
saposins in endosomes in vivo.
206 plore the in vivo functional interactions of
saposins in GSL metabolism and lysosomal storage disease
207 eate the tissue differential interactions of
saposins in GSL metabolism.
208 osaposin deletion mutants lacking individual
saposins in prosaposin-negative, CD1d-positive cells.
209 In addition, it is unclear whether
saposins,
in addition to loading, also promote dissociat
210 ion of cellular assays and demonstrated that
saposins influence CD1d-restricted presentation to human
211 To determine the
saposins involved in promoting lipid binding to CD1d, we
212 ighlight critical but different roles of the
saposin-
like and cytokine-like domains, including the th
213 cysteine mutations in the amino part of the
saposin-
like domain and in the base of the index finger
214 peptide SP-B(N), derived from the N-terminal
saposin-
like domain of the surfactant protein (SP)-B pro
215 The conserved regions include a
saposin-
like domain, proline-rich domain, and a putative
216 ly related, suggesting that all saposins and
saposin-
like domains share a common topology.
217 SP-B is a member of the
saposin-
like family of proteins, several of which have a
218 al structure of recombinant Mu8.1 displays a
saposin-
like fold and shows structural similarity with c
219 nment of deduced J3-crystallin indicates two
saposin-
like motifs arranged in tandem, each containing
220 ozoa, along with helminth parasites, utilize
saposin-
like PFTs prospectively for nutrient acquisition
221 xpression of Canopy2 (Cnpy2)/MIR-interacting
Saposin-
like protein (Msap) that is known to interact wi
222 t protein B (SP-B) proprotein contains three
saposin-
like protein (SAPLIP) domains: a SAPLIP domain c
223 Here, we identify Canopy4 (CNPY4), a
Saposin-
like protein, as a regulator of the HH pathway t
224 ilarity to the homologous regions of related
saposin-
like proteins and the importance of the distribu
225 intramolecular disulfide bonds shared by all
saposin-
like proteins.
226 omain with NK-lysin indicates that these two
saposin-
like structures are closely related, suggesting
227 ading lipid antigens without forming soluble
saposin-
lipid antigen complexes.
228 Here we present a
saposin-
lipoprotein nanoparticle system, Salipro, which
229 We suggest that
saposins mobilize monomeric lipids from lysosomal membra
230 Exon 3 encodes a circularly permutated
saposin motif, called a swaposin, found in plant asparti
231 bumins, nonspecific lipid transfer proteins,
saposins,
nematode polyprotein allergens/antigens).
232 Of the four mature
saposins,
only saposin C was found to increase sulfatide
233 ivery of prosaposin (PSAP), the precursor of
saposin peptides that are essential for lysosomal glycos
234 st a crystallin role for the multifunctional
saposin protein family in the jellyfish lens.
235 We found that saposin B forms soluble
saposin protein-lipid complexes detected by native gel e
236 ironment that is stabilized by a scaffold of
saposin proteins.
237 No individual
saposin proved to be absolutely essential, but the absen
238 The deficiency of prosaposin/
saposins (
PS-/-) in humans and mice leads to a decrease
239 he lipid antigen loading machinery genes pro-
saposin (
Psap), Niemann Pick type C2 (Npc2), alpha-galac
240 Importantly, we determined that similar to
saposins,
recombinant NPC2 was able to unload lipids fro
241 s and indicates that the putative primordial
saposin/
swaposin J3-crystallin reflects both the chapero
242 , in tandem, four glycoprotein activators or
saposins,
termed A, B, C, and D, that are essential for
243 espite high sequence homology among the four
saposins,
they have different specificities for lipid su
244 for understanding the contributions of this
saposin to GSL metabolism and homeostasis.
245 tuned over a wide pH range by adjusting the
saposin-
to-lipid stoichiometry, enabling maintenance of
246 These findings reveal how
saposins use different strategies to facilitate transfer
247 When recombinant exogenous
saposins were added to the prosaposin-negative cells, sa
248 We hypothesized that lysosomal
saposins,
which are cofactors required for sphingolipid
249 sing of full-length prosaposin to individual
saposins,
which are critical regulators of lysosomal sph
250 cystophora), shows similarity to vertebrate
saposins,
which are multifunctional proteins that bridge