A ubiquitin-interacting motif (UIM) is essential for Eps15 and Eps15R ubiquitination.

An important negative control mechanism in the signaling of epidermal growth factor (EGF) is the endocytosis and subsequent degradation of activated EGF receptors. Eps15 and its related partner Eps15R play a key role in clathrin-mediated endocytosis of transmembrane receptors. Upon EGF stimulation of the cell, Eps15 becomes both phosphorylated on tyrosine residues and monoubiquitinated.

Nuclear localization of phosphatidylinositol 4-kinase beta.

Whereas most phosphatidylinositol 4-kinase (PtdIns 4-kinase) activity is localized in the cytoplasm, PtdIns 4-kinase activity has also been detected in membrane-depleted nuclei of rat liver and mouse NIH 3T3 cells. Here we have characterized the PtdIns 4-kinase that is present in nuclei from NIH 3T3 cells. Both type II and type III PtdIns 4-kinase activity were observed in the detergent-insoluble fraction of NIH 3T3 cells.

Sphingolipids and cholesterol modulate membrane susceptibility to cytosolic phospholipase A(2).

Modulation of cytosolic phospholipase A(2) (cPLA(2)) activity by sphingomyelin (SPH), ceramide (Cer), and cholesterol (Chol) was investigated in CHO-2B cells activated by the calcium ionophore A23187 and epinephrine. Chol depletion of CHO-2B cells by treatment with methyl-beta-cyclodextrin (5 mm) resulted in the inhibition of the release of arachidonic acid whereas the restoration of the level by Chol-loaded cyclodextrin relieved inhibition. Conversion of CHO-2B cellular SPH to Cer by Staphylococcus aureus sphingomyelinase enhanced endogenous cPLA(2) activation as well as uptake by cells of C2- and C6-ceramide analogs.

N-terminal and C-terminal plasma membrane anchoring modulate differently agonist-induced activation of cytosolic phospholipase A2.

The 85 kDa cytosolic phospholipase A2 (cPLA2) plays a key role in liberating arachidonic acid from the sn-2 position of membrane phospholipids. When activated by extracellular stimuli, cPLA2 undergoes calcium-dependent translocation from cytosol to membrane sites which are still a matter of debate. In order to evaluate the effect of plasma membrane association on cPLA2 activation, we constructed chimeras of cPLA2 constitutively targeted to the plasma membrane by the N-terminal targeting sequence of the protein tyrosine kinase Lck (Lck-cPLA2) or the C-terminal targeting signal of K-Ras4B (cPLA2-Ras).