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An intrinsic lipid-binding interface controls sphingosine kinase 1 function.

ABSTRACT: Sphingosine kinase 1 (SK1) is required for production of sphingosine-1-phosphate (S1P) and thereby regulates many cellular processes, including cellular growth, immune cell trafficking, and inflammation. To produce S1P, SK1 must access sphingosine directly from membranes. However, the molecular mechanisms underlying SK1's direct membrane interactions remain unclear. We used hydrogen/deuterium exchange MS to study interactions of SK1 with membrane vesicles. Using the CRISPR/Cas9 technique to generate HCT116 cells lacking SK1, we explored the effects of membrane interface disruption and the function of the SK1 interaction site. Disrupting the interface resulted in reduced membrane association and decreased cellular SK1 activity. Moreover, SK1-dependent signaling, including cell invasion and endocytosis, was abolished upon mutation of the membrane-binding interface. Of note, we identified a positively charged motif on SK1 that is responsible for electrostatic interactions with membranes. Furthermore, we demonstrated that SK1 uses a single contiguous interface, consisting of an electrostatic site and a hydrophobic site, to interact with membrane-associated anionic phospholipids. Altogether, these results define a composite domain in SK1 that regulates its intrinsic ability to bind membranes and indicate that this binding is critical for proper SK1 function. This work will allow for a new line of thinking for targeting SK1 in disease.

SUBMITTER: Pulkoski-Gross MJ

PROVIDER: S-EPMC5832922 | biostudies-literature | 2018 Mar

REPOSITORIES: biostudies-literature

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An intrinsic lipid-binding interface controls sphingosine kinase 1 function.

Pulkoski-Gross Michael J MJ Jenkins Meredith L ML Truman Jean-Philip JP Salama Mohamed F MF Clarke Christopher J CJ Burke John E JE Hannun Yusuf A YA Obeid Lina M LM

Journal of lipid research 20180111 3

Sphingosine kinase 1 (SK1) is required for production of sphingosine-1-phosphate (S1P) and thereby regulates many cellular processes, including cellular growth, immune cell trafficking, and inflammation. To produce S1P, SK1 must access sphingosine directly from membranes. However, the molecular mechanisms underlying SK1's direct membrane interactions remain unclear. We used hydrogen/deuterium exchange MS to study interactions of SK1 with membrane vesicles. Using the CRISPR/Cas9 technique to gene ...[more]

PMID: 29326159

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Project description:Many immunoreceptors have cytoplasmic domains that are intrinsically disordered (i.e., have high configurational entropy), have multiple sites of posttranslational modification (e.g., tyrosine phosphorylation), and participate in nonlinear signaling pathways (e.g., exhibiting switch-like behavior). Several hypotheses to explain the origin of these nonlinearities fall under the broad hypothesis that modification at one site changes the immunoreceptor's entropy, which in turn changes further modification dynamics. Here, we use coarse-grain simulation to study three scenarios, all related to the chains that constitute the T cell receptor (TCR). We find that first, if phosphorylation induces local changes in the flexibility of the TCR ζ-chain, this naturally leads to rate enhancements and cooperativity. Second, we find that TCR CD3ɛ can provide a switch by modulating its residence in the plasma membrane. By constraining our model to be consistent with the previous observation that both basic residues and phosphorylation control membrane residence, we find that there is only a moderate rate enhancement of 10% between first and subsequent phosphorylation events. Third, we find that volume constraints do not limit the number of ZAP70s that can bind the TCR but that entropic penalties lead to a 200-fold decrease in binding rate by the seventh ZAP70, potentially explaining the observation that each TCR has around six ZAP70 molecules bound after receptor triggering. In all three scenarios, our results demonstrate that phenomena that change an immunoreceptor chain's entropy (stiffening, confinement to a membrane, and multiple simultaneous binding) can lead to nonlinearities (rate enhancement, switching, and negative cooperativity) in how the receptor participates in signaling. These polymer-entropy-driven nonlinearities may augment the nonlinearities that arise from, e.g., kinetic proofreading and cluster formation. They also suggest different design strategies for engineered receptors, e.g., whether or not to put signaling modules on one chain or multiple clustered chains.

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An intrinsic lipid-binding interface controls sphingosine kinase 1 function.

Publications

An intrinsic lipid-binding interface controls sphingosine kinase 1 function.

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