Identification and functional characterization of a novel Candida albicans gene CaMNN5 that suppresses the iron-dependent growth defect of Saccharomyces cerevisiae aft1Delta mutant.
In Saccharomyces cerevisiae, the transcription factor Aft1p plays a central role in regulating many genes involved in iron acquisition and utilization. An aft1Delta mutant exhibits severely retarded growth under iron starvation. To identify the functional counterpart of AFT1 in Candida albicans, we transformed a C. albicans genomic DNA library into aft1Delta to isolate genes that could allow the mutant to grow under iron-limiting conditions. In the present paper, we describe the unexpected discovery in this screen of CaMNN5. CaMnn5p is an alpha-1,2-mannosyltransferease, but its growth-promoting function in iron-limiting conditions does not require this enzymatic activity. Its function is also independent of the high-affinity iron transport systems that are mediated by Ftr1p and Fth1p. We obtained evidence suggesting that CaMnn5p may function along the endocytic pathway, because it cannot promote the growth of end4Delta and vps4Delta mutants, where the endocytic pathway is blocked at an early and late step respectively. Neither can it promote the growth of a fth1Delta smf3Delta mutant, where the vacuole-cytosol iron transport is blocked. Expression of CaMNN5 in S. cerevisiae specifically enhances an endocytosis-dependent mechanism of iron uptake without increasing the uptake of Lucifer Yellow, a marker for fluid-phase endocytosis. CaMnn5p contains three putative Lys-Glu-Xaa-Xaa-Glu iron-binding sites and co-immunoprecipitates with 55Fe. We propose that CaMnn5p promotes iron uptake and usage along the endocytosis pathway under iron-limiting conditions, a novel function that might have evolved in C. albicans.
Bai
Chen
C
Institute of Molecular and Cell Biology, Proteos, 61 Biopolis Drive, 138673, Singapore.
Chan
Fong Yee
FY
Wang
Yue
Y
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D001665:Binding Sites; D001692:Biological Transport; D002176:Candida albicans / Q000235:genetics* / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D003001:Cloning, Molecular; D004705:Endocytosis; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015966:Gene Expression Regulation, Fungal; D005800:Genes, Fungal / Q000235:genetics; D015698:Genomic Library; D007501:Iron / Q000378:metabolism* / Q000494:pharmacology; D000090463:Iron Deficiencies; D008364:Mannosyltransferases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D021381:Protein Transport; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics* / Q000378:metabolism; D013489:Suppression, Genetic / Q000235:genetics*; D014157:Transcription Factors / Q000172:deficiency / Q000235:genetics*
C090297:AFT1 protein, S cerevisiae; D002352:Carrier Proteins; D005656:Fungal Proteins; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D007501:Iron; D008364:Mannosyltransferases
Trends Microbiol. 2001 Aug;9(8):397-403
11514223
EMBO J. 1996 Jul 1;15(13):3377-84
8670839
Biochem J. 2002 Dec 1;368(Pt 2):641-7
12207560
J Infect Dis. 1973 Jun;127(6):705-8
4575002
Mol Gen Genet. 1984;198(2):179-82
6394964
Eur J Biochem. 1987 May 4;164(3):485-506
3032619
FEBS Lett. 1988 Apr 11;231(1):253-8
3282922
Mol Biol Cell. 1992 Jun;3(6):633-54
1379856
J Cell Biol. 1992 Nov;119(3):513-21
1400588
Cell. 1994 Jan 28;76(2):403-10
8293473
J Biol Chem. 1994 Oct 21;269(42):26092-9
7929320
EMBO J. 1995 Mar 15;14(6):1231-9
7720713
J Mol Biol. 1995 May 19;248(5):949-67
7760335
J Biol Chem. 1995 Nov 10;270(45):26723-6
7592901
Physiol Rev. 1996 Jan;76(1):31-47
8592731
Science. 1996 Mar 15;271(5255):1552-7
8599111
Mol Biol Cell. 1996 Apr;7(4):579-94
8730101
EMBO J. 1997 Apr 15;16(8):1820-31
9155008
Yeast. 1997 Jun 15;13(7):621-37
9200812
J Biol Chem. 1997 Nov 14;272(46):28933-8
9360964
Proc Natl Acad Sci U S A. 1998 Jul 7;95(14):7945-50
9653120
J Biol Chem. 1998 Aug 28;273(35):22181-7
9712830
J Biol Chem. 1998 Oct 9;273(41):26836-43
9756928
Microbiology. 1999 Sep;145 ( Pt 9):2415-22
10517594
J Biol Chem. 1999 Dec 3;274(49):35089-94
10574989
J Biol Chem. 1999 Dec 31;274(53):38061-70
10608875
Science. 2000 May 12;288(5468):1062-4
10807578
J Biol Chem. 2000 May 26;275(21):16354-9
10748025
Biometals. 2000 Mar;13(1):65-72
10831226
J Biol Chem. 2000 Jun 23;275(25):18933-8
10766761
Mol Cell Biol. 2000 Nov;20(21):7893-902
11027260
Cell. 2000 Sep 29;103(1):113-25
11051552
J Cell Sci. 2001 May;114(Pt 10):1935-47
11329380
J Biol Chem. 2001 Aug 3;276(31):29515-9
11390404
Proc Natl Acad Sci U S A. 2005 Jan 18;102(3):571-6
15598734
J Biol Chem. 2002 Aug 23;277(34):30598-605
12060662