Protein kinase A and C activities and endogenous substrates in ovine small and large luteal cells

Patricia B Hoyer, Wuyi Kong

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

Protein kinase A (cAMP-dependent) and C (calcium, phospholipid-dependent) activities were measured and in vitro phosphorylation of endogenous proteins by these kinases were observed by SDS-PAGE in 100000 × g supernatant (soluble) fractions of ovine small (12-22 μm) and large (> 22 μm) luteal cells. No differences in stimulation (P < 0.05) of A kinase activity between small and large cells were detected. Protein kinase C activity was stimulated (P < 0.05) 2.9-fold in small cells but not significantly enhanced above basal (P > 0.05) in large cells. By direct comparison, greater stimulation (P < 0.05) over basal of A versus C kinase (6.1- versus 2.9-fold) was measured in small cells. These stimulations were greater than those observed in large cells (A kinase, 4.8-fold; C kinase, 1.8-fold). Maximal specific activities of both kinases (per mg protein) were greater (P < 0.05) in small than in large cells. Endogenous proteins that could serve as substrates for phosphorylation by A and C kinases differed between small and large cells. Phosphorylation of six proteins by A kinase was consistently greater in small than in large cells. One endogenous protein (37 kDa) appeared to serve as a preferred substrate for phosphorylation by A kinase in small cells and C kinase in large cells. One protein (81 kDa) was predominantly phosphorylated in large rather than small cells by a calcium-dependent, C kinase-indepen- dent mechanism. These results support the accepted role of cAMP via A kinase and a possible role for C kinase in regulating Steroidogenesis in ovine small luteal cells. The inability of large cells to respond to cAMP with enhanced secretion of progesterone may be due to an unavailability of phosphoprotein substrates for A kinase. Furthermore, protein kinase C activity and available protein substrates display quantitative and qualitative differences between small and large cells. Differences in regulation of Steroidogenesis between the cell types may be due to these observed differences.

Original languageEnglish (US)
Pages (from-to)203-215
Number of pages13
JournalMolecular and Cellular Endocrinology
Volume62
Issue number2
DOIs
StatePublished - 1989

Fingerprint

Luteal Cells
Cyclic AMP-Dependent Protein Kinases
Protein Kinase C
Sheep
Phosphotransferases
Substrates
Phosphorylation
Proteins
Protein Kinases
Calcium
Phosphoproteins
Staphylococcal Protein A
Progesterone
Polyacrylamide Gel Electrophoresis
Phospholipids

Keywords

  • (Ovine corpus luteum)
  • Luteal cell type
  • Protein kinase
  • Steroidogenesis

ASJC Scopus subject areas

  • Endocrinology
  • Endocrinology, Diabetes and Metabolism

Cite this

Protein kinase A and C activities and endogenous substrates in ovine small and large luteal cells. / Hoyer, Patricia B; Kong, Wuyi.

In: Molecular and Cellular Endocrinology, Vol. 62, No. 2, 1989, p. 203-215.

Research output: Contribution to journalArticle

@article{23be63da853d4dc2a26ab91361be763a,
title = "Protein kinase A and C activities and endogenous substrates in ovine small and large luteal cells",
abstract = "Protein kinase A (cAMP-dependent) and C (calcium, phospholipid-dependent) activities were measured and in vitro phosphorylation of endogenous proteins by these kinases were observed by SDS-PAGE in 100000 × g supernatant (soluble) fractions of ovine small (12-22 μm) and large (> 22 μm) luteal cells. No differences in stimulation (P < 0.05) of A kinase activity between small and large cells were detected. Protein kinase C activity was stimulated (P < 0.05) 2.9-fold in small cells but not significantly enhanced above basal (P > 0.05) in large cells. By direct comparison, greater stimulation (P < 0.05) over basal of A versus C kinase (6.1- versus 2.9-fold) was measured in small cells. These stimulations were greater than those observed in large cells (A kinase, 4.8-fold; C kinase, 1.8-fold). Maximal specific activities of both kinases (per mg protein) were greater (P < 0.05) in small than in large cells. Endogenous proteins that could serve as substrates for phosphorylation by A and C kinases differed between small and large cells. Phosphorylation of six proteins by A kinase was consistently greater in small than in large cells. One endogenous protein (37 kDa) appeared to serve as a preferred substrate for phosphorylation by A kinase in small cells and C kinase in large cells. One protein (81 kDa) was predominantly phosphorylated in large rather than small cells by a calcium-dependent, C kinase-indepen- dent mechanism. These results support the accepted role of cAMP via A kinase and a possible role for C kinase in regulating Steroidogenesis in ovine small luteal cells. The inability of large cells to respond to cAMP with enhanced secretion of progesterone may be due to an unavailability of phosphoprotein substrates for A kinase. Furthermore, protein kinase C activity and available protein substrates display quantitative and qualitative differences between small and large cells. Differences in regulation of Steroidogenesis between the cell types may be due to these observed differences.",
keywords = "(Ovine corpus luteum), Luteal cell type, Protein kinase, Steroidogenesis",
author = "Hoyer, {Patricia B} and Wuyi Kong",
year = "1989",
doi = "10.1016/0303-7207(89)90007-5",
language = "English (US)",
volume = "62",
pages = "203--215",
journal = "Molecular and Cellular Endocrinology",
issn = "0303-7207",
publisher = "Elsevier Ireland Ltd",
number = "2",

}

TY - JOUR

T1 - Protein kinase A and C activities and endogenous substrates in ovine small and large luteal cells

AU - Hoyer, Patricia B

AU - Kong, Wuyi

PY - 1989

Y1 - 1989

N2 - Protein kinase A (cAMP-dependent) and C (calcium, phospholipid-dependent) activities were measured and in vitro phosphorylation of endogenous proteins by these kinases were observed by SDS-PAGE in 100000 × g supernatant (soluble) fractions of ovine small (12-22 μm) and large (> 22 μm) luteal cells. No differences in stimulation (P < 0.05) of A kinase activity between small and large cells were detected. Protein kinase C activity was stimulated (P < 0.05) 2.9-fold in small cells but not significantly enhanced above basal (P > 0.05) in large cells. By direct comparison, greater stimulation (P < 0.05) over basal of A versus C kinase (6.1- versus 2.9-fold) was measured in small cells. These stimulations were greater than those observed in large cells (A kinase, 4.8-fold; C kinase, 1.8-fold). Maximal specific activities of both kinases (per mg protein) were greater (P < 0.05) in small than in large cells. Endogenous proteins that could serve as substrates for phosphorylation by A and C kinases differed between small and large cells. Phosphorylation of six proteins by A kinase was consistently greater in small than in large cells. One endogenous protein (37 kDa) appeared to serve as a preferred substrate for phosphorylation by A kinase in small cells and C kinase in large cells. One protein (81 kDa) was predominantly phosphorylated in large rather than small cells by a calcium-dependent, C kinase-indepen- dent mechanism. These results support the accepted role of cAMP via A kinase and a possible role for C kinase in regulating Steroidogenesis in ovine small luteal cells. The inability of large cells to respond to cAMP with enhanced secretion of progesterone may be due to an unavailability of phosphoprotein substrates for A kinase. Furthermore, protein kinase C activity and available protein substrates display quantitative and qualitative differences between small and large cells. Differences in regulation of Steroidogenesis between the cell types may be due to these observed differences.

AB - Protein kinase A (cAMP-dependent) and C (calcium, phospholipid-dependent) activities were measured and in vitro phosphorylation of endogenous proteins by these kinases were observed by SDS-PAGE in 100000 × g supernatant (soluble) fractions of ovine small (12-22 μm) and large (> 22 μm) luteal cells. No differences in stimulation (P < 0.05) of A kinase activity between small and large cells were detected. Protein kinase C activity was stimulated (P < 0.05) 2.9-fold in small cells but not significantly enhanced above basal (P > 0.05) in large cells. By direct comparison, greater stimulation (P < 0.05) over basal of A versus C kinase (6.1- versus 2.9-fold) was measured in small cells. These stimulations were greater than those observed in large cells (A kinase, 4.8-fold; C kinase, 1.8-fold). Maximal specific activities of both kinases (per mg protein) were greater (P < 0.05) in small than in large cells. Endogenous proteins that could serve as substrates for phosphorylation by A and C kinases differed between small and large cells. Phosphorylation of six proteins by A kinase was consistently greater in small than in large cells. One endogenous protein (37 kDa) appeared to serve as a preferred substrate for phosphorylation by A kinase in small cells and C kinase in large cells. One protein (81 kDa) was predominantly phosphorylated in large rather than small cells by a calcium-dependent, C kinase-indepen- dent mechanism. These results support the accepted role of cAMP via A kinase and a possible role for C kinase in regulating Steroidogenesis in ovine small luteal cells. The inability of large cells to respond to cAMP with enhanced secretion of progesterone may be due to an unavailability of phosphoprotein substrates for A kinase. Furthermore, protein kinase C activity and available protein substrates display quantitative and qualitative differences between small and large cells. Differences in regulation of Steroidogenesis between the cell types may be due to these observed differences.

KW - (Ovine corpus luteum)

KW - Luteal cell type

KW - Protein kinase

KW - Steroidogenesis

UR - http://www.scopus.com/inward/record.url?scp=0024605363&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0024605363&partnerID=8YFLogxK

U2 - 10.1016/0303-7207(89)90007-5

DO - 10.1016/0303-7207(89)90007-5

M3 - Article

C2 - 2545489

AN - SCOPUS:0024605363

VL - 62

SP - 203

EP - 215

JO - Molecular and Cellular Endocrinology

JF - Molecular and Cellular Endocrinology

SN - 0303-7207

IS - 2

ER -