Changes in annexin (lipocortin) content in human amnion and chorion at parturition

Leslie Myatt, J. Hirth, W. V. Everson

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

Arachidonic acid is mobilized from fetal membrane phospholipids at parturition leading to increased production of oxytocic prostaglandins which may initiate or maintain myometrial contractions. Phospholipid mobilization requires activation of phospholipase A2 or C, both of which require calcium for activity. The annexins (lipocortins) are a superfamily of proteins which bind to calcium and phospholipids and thereby may alter phospholipase activity through two mechanisms: modulation of intracellular free Ca2+ concentrations or regulation of the accessibility of phospholipids to hydrolyzing enzymes. Using Western immunoblotting with monospecific polyclonal antibodies, annexins I-VI were identified in human amnion and chorion/decidua at term in tissues obtained from patients in labor or not in labor. Each annexin was present in two distinct pools: a pool which only associated with the membrane in the presence of calcium (calcium-dependent pool) and a calcium-independent pool that remained membrane bound in the presence of calcium chelators. Annexin I was present as two species, resolving at 36 kDa and 68 kDa. The total concentration of annexin I in both amnion and chorion/decidua was significantly decreased with labor, while the total concentration of annexin V in chorion significantly increased with labor. The size of individual pools of annexins also changed with labor: the calcium-dependent pool of annexins I and II in both amnion and chorion significantly decreased; the calcium-dependent pool of annexin V increased in chorion; and calcium-independent pools of annexin I in amnion and annexins I, II, and V in chorion significantly decreased with labor. The decrease in total annexin I concentration with labor in amnion reflects a substantial decrease (80-90%) in the pool tightly bound to the membrane in a calcium-independent manner. This striking change distinguishes annexin I as a potential candidate inhibitor which is specifically downregulated at parturition, potentially leading to increased access of phospholipases to substrate phospholipids and increased prostaglandin production at labor.

Original languageEnglish (US)
Pages (from-to)363-373
Number of pages11
JournalJournal of Cellular Biochemistry
Volume50
Issue number4
DOIs
StatePublished - 1992
Externally publishedYes

Fingerprint

Annexins
Chorion
Annexin A1
Amnion
Parturition
Calcium
Personnel
Phospholipids
Annexin A5
Annexin A2
Membranes
Decidua
Phospholipases
Prostaglandins
Annexin A6
Oxytocics
Extraembryonic Membranes
Uterine Contraction
Phospholipases A2
Type C Phospholipases

Keywords

  • amnion
  • annexin
  • calcium-phospholipid binding
  • chorion
  • lipocortin
  • membrane-protein interaction
  • phospholipase A
  • prostaglandin metabolism

ASJC Scopus subject areas

  • Biochemistry
  • Cell Biology

Cite this

Changes in annexin (lipocortin) content in human amnion and chorion at parturition. / Myatt, Leslie; Hirth, J.; Everson, W. V.

In: Journal of Cellular Biochemistry, Vol. 50, No. 4, 1992, p. 363-373.

Research output: Contribution to journalArticle

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