| Structural highlights
Function
[SLM1_YEAST] Together with SLM2, effector of the TORC2- and calcineurin-signaling pathways. Phosphorylated and activated by TORC2 under favorable growth conditions. Mediates actin polarization via inhibition of calcineurin-dependent transcription. Upon nutrient limitation or environmental stress, gets dephosphorylated by calcineurin. Dephosphorylation inhibits its interaction with TORC2, thereby antagonizing TORC2 signaling and mediating calcineurin-dependent actin depolarization. Also functions in heat-induced, calcineurin-mediated uracil permease (FUR4) endocytosis.[1] [2] [3] [4]
Publication Abstract from PubMed
BACKGROUND: Pleckstrin homology (PH) domains are common membrane-targeting modules and their best characterized ligands are a set of important signaling lipids that include phosphatidylinositol phosphates (PtdInsPs). PH domains recognize PtdInsPs through two distinct mechanisms that use different binding pockets on opposite sides of the beta-strands 1 and 2: i) a canonical binding site delimited by the beta1-beta2 and beta3-beta4loops and ii) a non-canonical binding site bordered by the beta1-beta2 and beta5-beta6loops. The PH domain-containing protein Slm1 from budding yeast Saccharomyces cerevisiae is required for actin cytoskeleton polarization and cell growth. We recently reported that this PH domain binds PtdInsPs and phosphorylated sphingolipids in a cooperative manner. PRINCIPAL FINDINGS: To study the structural basis for the Slm1-PH domain (Slm1-PH) specificity, we co-crystallized this domain with different soluble compounds that have structures analogous to anionic lipid head groups of reported Slm1 ligands: inositol 4-phosphate, which mimics phosphatidylinositol-4-phosphate (PtdIns(4)P), and phosphoserine as a surrogate for dihydrosphingosine 1-phosphate (DHS1-P). We found electron densities for the ligands within the so-called non-canonical binding site. An additional positively charged surface that contacts a phosphate group was identified next to the canonical binding site. CONCLUSIONS: Our results suggest that Slm1-PH utilizes a non-canonical binding site to bind PtdInsPs, similar to that described for the PH domains of beta-spectrin, Tiam1 and ArhGAP9. Additionally, Slm1-PH may have retained an active canonical site. We propose that the presence of both a canonical and a non-canonical binding pocket in Slm1-PH may account for the cooperative binding to PtdInsPs and DHS-1P.
Structural Analyses of the Slm1-PH Domain Demonstrate Ligand Binding in the Non-Canonical Site.,Anand K, Maeda K, Gavin AC PLoS One. 2012;7(5):e36526. Epub 2012 May 4. PMID:22574179[5]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Audhya A, Loewith R, Parsons AB, Gao L, Tabuchi M, Zhou H, Boone C, Hall MN, Emr SD. Genome-wide lethality screen identifies new PI4,5P2 effectors that regulate the actin cytoskeleton. EMBO J. 2004 Oct 1;23(19):3747-57. Epub 2004 Sep 16. PMID:15372071 doi:10.1038/sj.emboj.7600384
- ↑ Fadri M, Daquinag A, Wang S, Xue T, Kunz J. The pleckstrin homology domain proteins Slm1 and Slm2 are required for actin cytoskeleton organization in yeast and bind phosphatidylinositol-4,5-bisphosphate and TORC2. Mol Biol Cell. 2005 Apr;16(4):1883-900. Epub 2005 Feb 2. PMID:15689497 doi:E04-07-0564
- ↑ Mulet JM, Martin DE, Loewith R, Hall MN. Mutual antagonism of target of rapamycin and calcineurin signaling. J Biol Chem. 2006 Nov 3;281(44):33000-7. Epub 2006 Sep 7. PMID:16959779 doi:M604244200
- ↑ Bultynck G, Heath VL, Majeed AP, Galan JM, Haguenauer-Tsapis R, Cyert MS. Slm1 and slm2 are novel substrates of the calcineurin phosphatase required for heat stress-induced endocytosis of the yeast uracil permease. Mol Cell Biol. 2006 Jun;26(12):4729-45. PMID:16738335 doi:10.1128/MCB.01973-05
- ↑ Anand K, Maeda K, Gavin AC. Structural Analyses of the Slm1-PH Domain Demonstrate Ligand Binding in the Non-Canonical Site. PLoS One. 2012;7(5):e36526. Epub 2012 May 4. PMID:22574179 doi:10.1371/journal.pone.0036526
|
