The Isoform-Specific Region of the Na,K-ATPase Catalytic Subunit:  Role in Enzyme Kinetics and Regulation by Protein Kinase C†

The temporal pattern with which phorbol 12-myristate 13-acetate (PMA), an activator of protein kinase C (PKC), modulates parathyroid hormone (PTH)-responsive adenylyl cyclase (AC) was evaluated in a clonal osteoblast-like cell line (UMR-106). Brief (< or = 1 h) exposure of UMR-106 cells to PMA enhanced PTH stimulation of AC, whereas more prolonged PMA treatment decreased the PTH response, with maximum inhibition occurring at < or = 6 h. PMA treatment also resulted in initial activation followed by downregulation of PKC. Exposure of cells to 1,2-dioctanoyl-sn-glycerol, which activated but did not downregulate PKC, resulted in bidirectional modulation of PTH-responsive AC identical to that produced by PMA. Prolonged PMA exposure decreased PTH receptor number, as determined by radioligand binding studies, and reduced PTH receptor mRNA levels, assessed by Northern blot analysis. Forskolin activation of the catalytic subunit of AC was also decreased after prolonged PMA treatment. The results suggest that activation of PKC sequentially stimulates and then inhibits PTH responsiveness. Inhibition of the PTH response occurs by PKC actions exerted on the PTH receptor and the AC catalytic subunit.

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Critical role of the Isoform‐Specific Region in Na,K‐ATPase trafficking and Protein Kinase C‐dependent regulation

The FASEB Journal ◽

10.1096/fasebj.24.1_supplement.607.7 ◽

2010 ◽

Vol 24 (S1) ◽

Author(s):

Sandrine V Pierre ◽

Yoann Sottejeau ◽

Aude Belliard ◽

Marie‐Josee Duran ◽

Thomas A Pressley

Keyword(s):

Protein Kinase C ◽

Protein Kinase ◽

Critical Role ◽

Specific Region ◽

Kinase C

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Protein kinase C differentially modulates PTH- and PGE2-sensitive adenylate cyclase in osteoblast-like cells

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.1992.262.1.e87 ◽

1992 ◽

Vol 262 (1) ◽

pp. E87-E95

Author(s):

A. M. Freyaldenhoven ◽

G. E. Gutierrez ◽

M. D. Lifschitz ◽

M. S. Katz

Keyword(s):

Protein Kinase C ◽

Protein Kinase ◽

Adenylate Cyclase ◽

Enzyme Activation ◽

Catalytic Subunit ◽

Cyclase Activity ◽

Adenylate Cyclase Activity ◽

Osteosarcoma Cell ◽

Kinase C ◽

Umr 106

The effects of phorbol 12-myristate 13-acetate (PMA), a known activator of protein kinase C, on receptor-mediated stimulation of adenylate cyclase were evaluated in a rat osteosarcoma cell line (UMR-106) with the osteoblast phenotype. Pretreatment of UMR-106 cells with PMA increased parathyroid hormone (PTH)-stimulated adenylate cyclase activity and inhibited prostaglandin E2 (PGE2)-responsive enzyme activity. In addition, PMA enhanced enzyme activation by forskolin, which is thought to exert a direct stimulatory action on the catalytic subunit of adenylate cyclase. The regulatory effects of PMA were concentration dependent and of rapid onset (less than or equal to 1 min). Treatment with PMA also resulted in translocation of protein kinase C activity from the cytosol to the particulate cell fraction. Pertussis toxin, which attenuates inhibition of adenylate cyclase mediated by the inhibitory guanine nucleotide-binding regulatory protein (Gi), augmented PTH-sensitive adenylate cyclase activity and reduced the incremental increase in PTH response produced by PMA. The results suggest that activation of protein kinase C increases PTH-stimulated adenylate cyclase activity by actions on Gi and/or the catalytic subunit and decreases PGE2 responsiveness by a mechanism involving the PGE2 receptor.

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Proteolysis of protein kinase C: mM and μM calcium-requiring calpains have different abilities to generate, and degrade the free catalytic subunit, protein kinase M

FEBS Letters ◽

10.1016/0014-5793(95)00543-i ◽

1995 ◽

Vol 367 (3) ◽

pp. 223-227 ◽

Cited By ~ 53

Author(s):

Corinne M. Cressman ◽

Panaiyur S. Mohan ◽

Ralph A. Nixon ◽

Thomas B. Shea

Keyword(s):

Protein Kinase C ◽

Protein Kinase ◽

Catalytic Subunit ◽

Subunit Protein ◽

Kinase C

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Effects of phosphorylation of the neurofilament L protein on filamentous structures.

Cell Regulation ◽

10.1091/mbc.1.2.237 ◽

1990 ◽

Vol 1 (2) ◽

pp. 237-248 ◽

Cited By ~ 78

Author(s):

S Hisanaga ◽

Y Gonda ◽

M Inagaki ◽

A Ikai ◽

N Hirokawa

Keyword(s):

Protein Kinase C ◽

Protein Kinase ◽

Chain Complex ◽

Catalytic Subunit ◽

Dependent Protein Kinase ◽

L Protein ◽

Camp Dependent Protein Kinase ◽

Kinase C ◽

Dependent Protein ◽

Favorable Conditions

Effects of phosphorylation of the neurofilament L protein (NF-L) on the reassembly system were studied by both sedimentation experiments and low-angle rotary shadowing. Bovine spinal cord NF-L was phosphorylated with 3-4 mol/mol protein by either the catalytic subunit of cAMP-dependent protein kinase or protein kinase C. Phosphorylated NF-L could not assemble into filaments. Phosphorylation by either cAMP-dependent protein kinase or protein kinase C inhibited the same step of the reassembly process. Phosphorylated NF-L remained as an 8-chain complex even in favorable conditions for reassembly. The extent of the effect of phosphorylation on the filamentous structure of NF-L was also investigated by using the catalytic subunit of cAMP-dependent protein kinase. The amount of unassembled NF-L increased linearly with increased phosphorylation in the sedimentation experiments. Structural observations indicated that 1 or 2 mol of phosphorylation is enough to inhibit reassembly and to induce disassembly, and the disassembly process was also observed. The filaments were shown to unravel with disassembly. Star-like clusters, which we reported as being the initial stage of reassembly, were also identified.

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