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Phosphoinositide kinase signaling controls ER-PM cross-talk.

Omnus DJ, Manford AG, Bader JM, Emr SD, Stefan CJ - Mol. Biol. Cell (2016)

Bottom Line: However, little is known about the sensory mechanisms for detecting membrane composition and how lipid metabolism is regulated in response to membrane stress.We find that phosphoinositide (PI) kinase signaling controls a conserved PDK-TORC2-Akt signaling cascade as part of a homeostasis network that allows the endoplasmic reticulum (ER) to modulate essential responses, including Ca(2+)-regulated lipid biogenesis, upon plasma membrane (PM) stress.Furthermore, loss of ER-PM junctions impairs this protective response, leading to PM integrity defects upon heat stress.

View Article: PubMed Central - PubMed

Affiliation: MRC Laboratory for Molecular Cell Biology, University College London, London WC1E 6BT, United Kingdom.

No MeSH data available.


Related in: MedlinePlus

PI4P and PI(4,5)P2 metabolism control TORC2 signaling. (A) TORC2 signaling and Slt2 MAPK phosphorylation in wild-type, stt4ts, and mss4ts cells. Wild-type (WT), stt4ts, and mss4ts cells were incubated at 26 or 38°C for 2 h. Protein extracts were analyzed by immunoblotting using antisera that recognize phospho-Ypk1(T662) or phospho-Slt2. Quantifications below the blot report the difference relative to WT after normalizing to a protein loading control; results are the mean of three independent experiments. (B) TORC2 signaling and Slt2 MAPK phosphorylation in cells lacking the PI4P phosphatase Sac1 or the ER-PM tether proteins. WT, sac1Δ, and Δtether cells were incubated at 26 or 38°C for 2 h. Protein extracts were analyzed by immunoblotting using antisera that recognize phospho-Ypk1(T662) or phospho-Slt2. Quantifications below the blot report the difference relative to WT after normalizing to a protein loading control; results are the mean of three independent experiments. See Supplemental Figure S5. (C) Slm1-GFP localization in WT cells (left) and Δtether cells (right). Bottom, differential interference contrast overlays. Scale bar, 5 μm.
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Figure 5: PI4P and PI(4,5)P2 metabolism control TORC2 signaling. (A) TORC2 signaling and Slt2 MAPK phosphorylation in wild-type, stt4ts, and mss4ts cells. Wild-type (WT), stt4ts, and mss4ts cells were incubated at 26 or 38°C for 2 h. Protein extracts were analyzed by immunoblotting using antisera that recognize phospho-Ypk1(T662) or phospho-Slt2. Quantifications below the blot report the difference relative to WT after normalizing to a protein loading control; results are the mean of three independent experiments. (B) TORC2 signaling and Slt2 MAPK phosphorylation in cells lacking the PI4P phosphatase Sac1 or the ER-PM tether proteins. WT, sac1Δ, and Δtether cells were incubated at 26 or 38°C for 2 h. Protein extracts were analyzed by immunoblotting using antisera that recognize phospho-Ypk1(T662) or phospho-Slt2. Quantifications below the blot report the difference relative to WT after normalizing to a protein loading control; results are the mean of three independent experiments. See Supplemental Figure S5. (C) Slm1-GFP localization in WT cells (left) and Δtether cells (right). Bottom, differential interference contrast overlays. Scale bar, 5 μm.

Mentions: The yeast protein kinases 1 and 2 (Ypk1/2), orthologues of mammalian Akt, regulate sphingolipid synthesis in the ER. Ypk1/2 phosphorylate and inactivate the Orm1/2 proteins, integral ER membrane proteins that inhibit SPT, the first enzyme in sphingolipid biosynthesis (Roelants et al., 2011; Berchtold et al., 2012; Sun et al., 2012; Gururaj et al., 2013). Ypk1/2 also phosphorylate and activate ceramide synthases in the ER (Muir et al., 2014). Activation of Ypk1/2 occurs through two upstream protein kinases, the PDK orthologues Pkh1/Pkh2 and TORC2; Roelants et al., 2004; Niles et al., 2012). TORC2 signaling in yeast cells is regulated by the PI(4,5)P2-binding Slm1 and Slm2 proteins (Audhya et al., 2004; see later discussion of Figure 5). However, it is unclear whether PI kinase signaling regulates the yeast PDK orthologues Pkh1 and Pkh2.


Phosphoinositide kinase signaling controls ER-PM cross-talk.

Omnus DJ, Manford AG, Bader JM, Emr SD, Stefan CJ - Mol. Biol. Cell (2016)

PI4P and PI(4,5)P2 metabolism control TORC2 signaling. (A) TORC2 signaling and Slt2 MAPK phosphorylation in wild-type, stt4ts, and mss4ts cells. Wild-type (WT), stt4ts, and mss4ts cells were incubated at 26 or 38°C for 2 h. Protein extracts were analyzed by immunoblotting using antisera that recognize phospho-Ypk1(T662) or phospho-Slt2. Quantifications below the blot report the difference relative to WT after normalizing to a protein loading control; results are the mean of three independent experiments. (B) TORC2 signaling and Slt2 MAPK phosphorylation in cells lacking the PI4P phosphatase Sac1 or the ER-PM tether proteins. WT, sac1Δ, and Δtether cells were incubated at 26 or 38°C for 2 h. Protein extracts were analyzed by immunoblotting using antisera that recognize phospho-Ypk1(T662) or phospho-Slt2. Quantifications below the blot report the difference relative to WT after normalizing to a protein loading control; results are the mean of three independent experiments. See Supplemental Figure S5. (C) Slm1-GFP localization in WT cells (left) and Δtether cells (right). Bottom, differential interference contrast overlays. Scale bar, 5 μm.
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Figure 5: PI4P and PI(4,5)P2 metabolism control TORC2 signaling. (A) TORC2 signaling and Slt2 MAPK phosphorylation in wild-type, stt4ts, and mss4ts cells. Wild-type (WT), stt4ts, and mss4ts cells were incubated at 26 or 38°C for 2 h. Protein extracts were analyzed by immunoblotting using antisera that recognize phospho-Ypk1(T662) or phospho-Slt2. Quantifications below the blot report the difference relative to WT after normalizing to a protein loading control; results are the mean of three independent experiments. (B) TORC2 signaling and Slt2 MAPK phosphorylation in cells lacking the PI4P phosphatase Sac1 or the ER-PM tether proteins. WT, sac1Δ, and Δtether cells were incubated at 26 or 38°C for 2 h. Protein extracts were analyzed by immunoblotting using antisera that recognize phospho-Ypk1(T662) or phospho-Slt2. Quantifications below the blot report the difference relative to WT after normalizing to a protein loading control; results are the mean of three independent experiments. See Supplemental Figure S5. (C) Slm1-GFP localization in WT cells (left) and Δtether cells (right). Bottom, differential interference contrast overlays. Scale bar, 5 μm.
Mentions: The yeast protein kinases 1 and 2 (Ypk1/2), orthologues of mammalian Akt, regulate sphingolipid synthesis in the ER. Ypk1/2 phosphorylate and inactivate the Orm1/2 proteins, integral ER membrane proteins that inhibit SPT, the first enzyme in sphingolipid biosynthesis (Roelants et al., 2011; Berchtold et al., 2012; Sun et al., 2012; Gururaj et al., 2013). Ypk1/2 also phosphorylate and activate ceramide synthases in the ER (Muir et al., 2014). Activation of Ypk1/2 occurs through two upstream protein kinases, the PDK orthologues Pkh1/Pkh2 and TORC2; Roelants et al., 2004; Niles et al., 2012). TORC2 signaling in yeast cells is regulated by the PI(4,5)P2-binding Slm1 and Slm2 proteins (Audhya et al., 2004; see later discussion of Figure 5). However, it is unclear whether PI kinase signaling regulates the yeast PDK orthologues Pkh1 and Pkh2.

Bottom Line: However, little is known about the sensory mechanisms for detecting membrane composition and how lipid metabolism is regulated in response to membrane stress.We find that phosphoinositide (PI) kinase signaling controls a conserved PDK-TORC2-Akt signaling cascade as part of a homeostasis network that allows the endoplasmic reticulum (ER) to modulate essential responses, including Ca(2+)-regulated lipid biogenesis, upon plasma membrane (PM) stress.Furthermore, loss of ER-PM junctions impairs this protective response, leading to PM integrity defects upon heat stress.

View Article: PubMed Central - PubMed

Affiliation: MRC Laboratory for Molecular Cell Biology, University College London, London WC1E 6BT, United Kingdom.

No MeSH data available.


Related in: MedlinePlus