WBsf919669

Caenorhabditis elegans

lin-11 pi enhancer region

pifk

PhosphoInositide Four Kinase (PI-4 Kinase)

JH3055

Caenorhabditis elegans

Cockcroft S et al. (2016) Biochem Soc Trans "RdgB reciprocally transfers PA and PI at ER-PM contact sites to maintain PI(4,5)P2 homoeostasis during phospholipase C signalling in Drosophila photoreceptors."

Cockcroft S, Raghu P, Garner K, Gomez-Espinoza E, Yadav S

[Biochem Soc Trans, 2016]

Phosphatidylinositol (PI) is the precursor lipid for the synthesis of PI 4,5-bisphosphate [PI(4,5)P2] at the plasma membrane (PM) and is sequentially phosphorylated by the lipid kinases, PI 4-kinase and phosphatidylinositol 4-phosphate (PI4P)-5-kinase. Receptor-mediated hydrolysis of PI(4,5)P2 takes place at the PM but PI resynthesis occurs at the endoplasmic reticulum (ER). Thus PI(4,5)P2 resynthesis requires the reciprocal transport of two key intermediates, phosphatidic acid (PA) and PI between the ER and the PM. PI transfer proteins (PITPs), defined by the presence of the PITP domain, can facilitate lipid transfer between membranes; the PITP domain comprises a hydrophobic cavity with dual specificity but accommodates a single phospholipid molecule. The class II PITP, retinal degeneration typeB (RdgB) is a multi-domain protein and its PITP domain can bind and transfer PI and PA. In Drosophila photoreceptors, a well-defined G-protein-coupled phospholipase C (PLC) signalling pathway, phototransduction defects resulting from loss of RdgB can be rescued by expression of the PITP domain provided it is competent for both PI and PA transfer. We propose that RdgB proteins maintain PI(4,5)P2 homoeostasis after PLC activation by facilitating the reciprocal transport of PA and PI at ER-PM membrane contact sites.

Banerjee S et al. (2015) PLoS One "Imaging Cellular Inorganic Phosphate in Caenorhabditis elegans Using a Genetically Encoded FRET-Based Biosensor."

Versaw WK, Banerjee S, Garcia LR

[PLoS One, 2015]

Inorganic phosphate (Pi) has central roles in metabolism, cell signaling and energy conversion. The distribution of Pi to each cell and cellular compartment of an animal must be tightly coordinated with its dietary supply and with the varied metabolic demands of individual cells. An analytical method for monitoring Pi dynamics with spatial and temporal resolution is therefore needed to gain a comprehensive understanding of mechanisms governing the transport and recycling of this essential nutrient. Here we demonstrate the utility of a genetically encoded FRET-based Pi sensor to assess cellular Pi levels in the nematode Caenorhabditis elegans. The sensor was expressed in different cells and tissues of the animal, including head neurons, tail neurons, pharyngeal muscle, and the intestine. Cytosolic Pi concentrations were monitored using ratiometric imaging. Injection of phosphate buffer into intestinal cells confirmed that the sensor was responsive to changes in Pi concentration in vivo. Live Pi imaging revealed cell-specific and developmental stage-specific differences in cytosolic Pi concentrations. In addition, cellular Pi levels were perturbed by food deprivation and by exposure to the respiratory inhibitor cyanide. These results suggest that Pi concentration is a sensitive indicator of metabolic status. Moreover, we propose that live Pi imaging in C. elegans is a powerful approach to discern mechanisms that govern Pi distribution in individual cells and throughout an animal.

Maekawa M et al. (2014) Proc Natl Acad Sci U S A "Sequential breakdown of 3-phosphorylated phosphoinositides is essential for the completion of macropinocytosis."

Mochizuki Y, Ikeda Y, Araki N, Terasaka S, Arai H, Taguchi T, Skolnik EY, Maekawa M, Kawai K

[Proc Natl Acad Sci U S A, 2014]

Macropinocytosis is a highly conserved endocytic process by which extracellular fluid and solutes are internalized into cells. Macropinocytosis starts with the formation of membrane ruffles at the plasma membrane and ends with their closure. The transient and sequential emergence of phosphoinositides PI(3,4,5)P3 and PI(3,4)P2 in the membrane ruffles is essential for macropinocytosis. By making use of information in the Caenorhabditis elegans mutants defective in fluid-phase endocytosis, we found that mammalian phosphoinositide phosphatase MTMR6 that dephosphorylates PI(3)P to PI, and its binding partner MTMR9, are required for macropinocytosis. INPP4B, which dephosphorylates PI(3,4)P2 to PI(3)P, was also found to be essential for macropinocytosis. These phosphatases operate after the formation of membrane ruffles to complete macropinocytosis. Finally, we showed that KCa3.1, a Ca(2+)-activated K(+) channel that is activated by PI(3)P, is required for macropinocytosis. We propose that the sequential breakdown of PI(3,4,5)P3 PI(3,4)P2 PI(3)P PI controls macropinocytosis through specific effectors of the intermediate phosphoinositides.

uterine pi cell (5L)

uterine pi cell that follows the 5L configuration of development.

uterine pi cell (5R)

uterine pi cell that follows the 5R configuration of development.

WBAntibody00002419

sun-1 antibodies directed against the phosphoepitope of Ser12 (S12-Pi) sun-1

WBAntibody00002418

sun-1 antibodies directed against the phosphoepitope of Ser8 (S8-Pi) sun-1