Tài liệu Báo cáo khoa học: Modulation of sterol homeostasis by the Cdc42p effectors Cla4p and Ste20p

Modulation of sterol homeostasis by the Cdc42p effectors

Cla4p and Ste20p in the yeast Saccharomyces cerevisiae

Meng Lin1,*, Karlheinz Grillitsch2,*, Gu¨ nther Daum2

, Ursula Just1 and Thomas Ho¨ fken1

1 Institute of Biochemistry, Christian Albrecht University, Kiel, Germany

2 Institute of Biochemistry, Graz University of Technology, Austria

Keywords

cell polarity; p21-activated kinase; sterol;

steryl ester; yeast

Correspondence

T. Ho¨fken, Institute of Biochemistry,

Christian Albrecht University Kiel,

Olshausenstrasse 40, 24098 Kiel, Germany

Fax: +49 431 8802609

Tel.: +49 431 8801660

E-mail: [email protected]

*These authors contributed equally to this

work

(Received 2 September 2009, revised 29

September 2009, accepted 12 October

2009)

doi:10.1111/j.1742-4658.2009.07433.x

The conserved Rho-type GTPase Cdc42p is a key regulator of signal trans￾duction and polarity in eukaryotic cells. In the yeast Saccharomyces cerevi￾siae, Cdc42p promotes polarized growth through the p21-activated kinases

Ste20p and Cla4p. Previously, we demonstrated that Ste20p forms a com￾plex with Erg4p, Cbr1p and Ncp1p, which all catalyze important steps in

sterol biosynthesis. CLA4 interacts genetically with ERG4 and NCP1. Fur￾thermore, Erg4p, Ncp1p and Cbr1p play important roles in cell polariza￾tion during vegetative growth, mating and filamentation. As Ste20p and

Cla4p are involved in these processes it seems likely that sterol biosynthetic

enzymes and p21-activated kinases act in related pathways. Here, we

demonstrate that the deletion of either STE20 or CLA4 results in increased

levels of sterols. In addition, higher concentrations of steryl esters, the stor￾age form of sterols, were observed in cla4D cells. CLA4 expression from a

multicopy plasmid reduces enzyme activity of Are2p, the major steryl ester

synthase, under aerobic conditions. Altogether, our data suggest that

Ste20p and Cla4p may function as negative modulators of sterol biosyn￾thesis. Moreover, Cla4p has a negative effect on steryl ester formation.

As sterol homeostasis is crucial for cell polarization, Ste20p and Cla4p

may regulate cell polarity in part through the modulation of sterol

homeostasis.

Structured digital abstract

l MINT-7291456: STE20 (uniprotkb:Q03497) physically interacts (MI:0915) with CBR1

(uniprotkb:P38626) by ubiquitin reconstruction (MI:0112)

l MINT-7291480: STE20 (uniprotkb:Q03497) physically interacts (MI:0915) with BEM1

(uniprotkb:P29366) by ubiquitin reconstruction (MI:0112)

l MINT-7291468: STE20 (uniprotkb:Q03497) physically interacts (MI:0915) with NCP1

(uniprotkb:P16603) by ubiquitin reconstruction (MI:0112)

l MINT-7291441: STE20 (uniprotkb:Q03497) physically interacts (MI:0915) with ERG4

(uniprotkb:P25340) by ubiquitin reconstruction (MI:0112)

l MINT-7291492: CLA4 (uniprotkb:P48562) physically interacts (MI:0915) with BEM1

(uniprotkb:P29366) by ubiquitin reconstruction (MI:0112)

l MINT-7291412: STE20 (uniprotkb:Q03497) physically interacts (MI:0915) with ARE1

(uniprotkb:P25628) by pull down (MI:0096)

l MINT-7291424: STE20 (uniprotkb:Q03497) physically interacts (MI:0915) with ARE2

(uniprotkb:P53629) by pull down (MI:0096)

Abbreviations

GST, glutathione S-transferase; PAK, p21-activated kinase; SC, synthetic complete; SE, steryl esters; YPD, 1% yeast extract, 2% peptone,

2% dextrose.

FEBS Journal 276 (2009) 7253–7264 ª 2009 The Authors Journal compilation ª 2009 FEBS 7253