Inhibition by phospholipids, lysophospholipids and gangliosides of melittin-induced phosphorylation in bovine mammary gland

Similarities of Cow Mammary Gland Cytosolic 21-kDa Protein, the Substrate for Protein Kinase C, to the 20-kDa Myosin Light Chain from Smooth Muscle

“…Melittin inhibited phosphorylation of the PKC and/or MLCK substrates, including that of the 21-kDa protein (lane 3). In contrast to the PKC/MLCK substrates, phosphorylation of 27-kDa, 24-kDa and 19-kDa proteins, the substrates for melittin-activated protein kinase [10,11] and sphingosine-activated protein kinase [9], were inversely enhanced by melittin. Melittin still inhibited the PKC/MLCK substrates, whereas it enhanced the 27-kDa, 24-kDa and 19-kDa protein phosphorylation, even when calmodulin and the PKC cofactors were included (lane 5).…”

“…The 21-kDa protein phosphorylation is inhibited by sphingosine [9], melittin [10,11], gangliosides [12] and sulfatide [14], and their inhibition is reversed by the excess addition of PS, but not by OAG or Ca 2+ . The 21-kDa protein is inferred to be a 20-kDa regulatory MLC from smooth muscle (MLC20) because of its molecular mass, its distribution in myoepithelial cell cytosol [3,29,37], its interaction with melittin [21,25], and as a substrate for PKC [6] as well as for Ca 2+ /calmodulin-dependent myosin light chain kinase (MLCK) [3,21,32].…”

Similarities of Cow Mammary Gland Cytosolic 21-kDa Protein, the Substrate for Protein Kinase C, to the 20-kDa Myosin Light Chain from Smooth Muscle

“…Melittin inhibited phosphorylation of the PKC and/or MLCK substrates, including that of the 21-kDa protein (lane 3). In contrast to the PKC/MLCK substrates, phosphorylation of 27-kDa, 24-kDa and 19-kDa proteins, the substrates for melittin-activated protein kinase [10,11] and sphingosine-activated protein kinase [9], were inversely enhanced by melittin. Melittin still inhibited the PKC/MLCK substrates, whereas it enhanced the 27-kDa, 24-kDa and 19-kDa protein phosphorylation, even when calmodulin and the PKC cofactors were included (lane 5).…”

“…The 21-kDa protein phosphorylation is inhibited by sphingosine [9], melittin [10,11], gangliosides [12] and sulfatide [14], and their inhibition is reversed by the excess addition of PS, but not by OAG or Ca 2+ . The 21-kDa protein is inferred to be a 20-kDa regulatory MLC from smooth muscle (MLC20) because of its molecular mass, its distribution in myoepithelial cell cytosol [3,29,37], its interaction with melittin [21,25], and as a substrate for PKC [6] as well as for Ca 2+ /calmodulin-dependent myosin light chain kinase (MLCK) [3,21,32].…”

Modulation by Sphingosine of Phosphorylation of Substrate Proteins by Protein Kinase C in Nuclei from Cow Mammary Gland

“…The 20-kDa protein was inferred to be the cytosolic 21-kDa smooth muscle myosin light chain (MLC20) [19]. The 19-kDa protein seemed to be the substrate for sphingosine- [13] or melittin-activated protein kinase [14,15]. Other than the PKC substrates, the 97-kDa protein appeared to be the substrate for phosphorylase b kinase [13].…”

Inhibition by Melittin of Phosphorylation by Protein Kinase C of Annexin I from Cow Mammary Gland.

“…Annexin I is not the substrate of the calmodulin-dependent enzyme [30]. Melittin activates a protein kinase in the mammary gland [17,18]. This protein kinase is distinct from PKC, because the stimulatory effect of melittin on the kinase is suppressed by PS [17,18], whereas the inhibitory effect of melittin on PKC is restored by PS (Fig.…”

Similarities of Cow Mammary Gland Cytosolic 21-kDa Protein, the Substrate for Protein Kinase C, to the 20-kDa Myosin Light Chain from Smooth Muscle

“…Melittin inhibited phosphorylation of the PKC and/or MLCK substrates, including that of the 21-kDa protein (lane 3). In contrast to the PKC/MLCK substrates, phosphorylation of 27-kDa, 24-kDa and 19-kDa proteins, the substrates for melittin-activated protein kinase [10,11] and sphingosine-activated protein kinase [9], were inversely enhanced by melittin. Melittin still inhibited the PKC/MLCK substrates, whereas it enhanced the 27-kDa, 24-kDa and 19-kDa protein phosphorylation, even when calmodulin and the PKC cofactors were included (lane 5).…”

“…The 21-kDa protein phosphorylation is inhibited by sphingosine [9], melittin [10,11], gangliosides [12] and sulfatide [14], and their inhibition is reversed by the excess addition of PS, but not by OAG or Ca 2+ . The 21-kDa protein is inferred to be a 20-kDa regulatory MLC from smooth muscle (MLC20) because of its molecular mass, its distribution in myoepithelial cell cytosol [3,29,37], its interaction with melittin [21,25], and as a substrate for PKC [6] as well as for Ca 2+ /calmodulin-dependent myosin light chain kinase (MLCK) [3,21,32].…”

Modulation by Sphingosine of Phosphorylation of Substrate Proteins by Protein Kinase C in Nuclei from Cow Mammary Gland

“…The 20-kDa protein was inferred to be the cytosolic 21-kDa smooth muscle myosin light chain (MLC20) [19]. The 19-kDa protein seemed to be the substrate for sphingosine- [13] or melittin-activated protein kinase [14,15]. Other than the PKC substrates, the 97-kDa protein appeared to be the substrate for phosphorylase b kinase [13].…”

Inhibition by Melittin of Phosphorylation by Protein Kinase C of Annexin I from Cow Mammary Gland.

“…Annexin I is not the substrate of the calmodulin-dependent enzyme [30]. Melittin activates a protein kinase in the mammary gland [17,18]. This protein kinase is distinct from PKC, because the stimulatory effect of melittin on the kinase is suppressed by PS [17,18], whereas the inhibitory effect of melittin on PKC is restored by PS (Fig.…”

Similarities of Cow Mammary Gland Cytosolic 21-kDa Protein, the Substrate for Protein Kinase C, to the 20-kDa Myosin Light Chain from Smooth Muscle

“…Melittin inhibited phosphorylation of the PKC and/or MLCK substrates, including that of the 21-kDa protein (lane 3). In contrast to the PKC/MLCK substrates, phosphorylation of 27-kDa, 24-kDa and 19-kDa proteins, the substrates for melittin-activated protein kinase [10,11] and sphingosine-activated protein kinase [9], were inversely enhanced by melittin. Melittin still inhibited the PKC/MLCK substrates, whereas it enhanced the 27-kDa, 24-kDa and 19-kDa protein phosphorylation, even when calmodulin and the PKC cofactors were included (lane 5).…”

“…The 21-kDa protein phosphorylation is inhibited by sphingosine [9], melittin [10,11], gangliosides [12] and sulfatide [14], and their inhibition is reversed by the excess addition of PS, but not by OAG or Ca 2+ . The 21-kDa protein is inferred to be a 20-kDa regulatory MLC from smooth muscle (MLC20) because of its molecular mass, its distribution in myoepithelial cell cytosol [3,29,37], its interaction with melittin [21,25], and as a substrate for PKC [6] as well as for Ca 2+ /calmodulin-dependent myosin light chain kinase (MLCK) [3,21,32].…”

Modulation by Sphingosine of Phosphorylation of Substrate Proteins by Protein Kinase C in Nuclei from Cow Mammary Gland

“…The 20-kDa protein was inferred to be the cytosolic 21-kDa smooth muscle myosin light chain (MLC20) [19]. The 19-kDa protein seemed to be the substrate for sphingosine- [13] or melittin-activated protein kinase [14,15]. Other than the PKC substrates, the 97-kDa protein appeared to be the substrate for phosphorylase b kinase [13].…”

Inhibition by Melittin of Phosphorylation by Protein Kinase C of Annexin I from Cow Mammary Gland.

“…Annexin I is not the substrate of the calmodulin-dependent enzyme [30]. Melittin activates a protein kinase in the mammary gland [17,18]. This protein kinase is distinct from PKC, because the stimulatory effect of melittin on the kinase is suppressed by PS [17,18], whereas the inhibitory effect of melittin on PKC is restored by PS (Fig.…”