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Calmodulin in starfish oocytes. II. Trypsin treatment suppresses the trifluoperazine-sensitive step
Abstract:
The 1-methyladenine-induced oocyte maturation in starfish is reversibly inhibited by the anticalmodulin drug, trifluoperazine (TFP). However, when oocytes are exposed for 10 min to trypsin, they lose their sensitivity to TFP. Trypsin does not alter the length of the hormone-dependent period (1-methyladenine minimal contact time) or the 1-methyladenine concentration requirements. Trypsin-treated oocytes remain sensitive to other maturation inhibitors such as procaine, theophylline, caffeine, and D-600. Trypsin exposure modifies the protein pattern composition of the oocyte cortex (breakdown of a 140-kDa protein). TFP binding site localization was studied using fluorescence microscopy: in addition to a general diffuse fluorescence, staining is localized to probably acidic granules located in the cortex. Results are discussed in relation to calmodulin and plasma membrane calmodulin-dependent enzyme involvement in the stimulation of starfish oocyte maturation.
Insights
Starfish oocyte maturation is inhibited by trifluoperazine (TFP), but trypsin treatment removes this sensitivity by altering the oocyte cortex. This suggests calmodulin
Area of Science:
- * Reproductive biology
- * Cell signaling
- * Biochemistry
Background:
- * 1-methyladenine (1-MeA) is a hormone that induces oocyte maturation in starfish.
- * Anticalmodulin drugs like trifluoperazine (TFP) reversibly inhibit this process.
- * The precise mechanisms of TFP action and potential regulatory pathways are not fully understood.
Purpose of the Study:
- * To investigate the mechanism by which trypsin exposure alters starfish oocyte sensitivity to TFP.
- * To explore the role of calmodulin and calmodulin-dependent enzymes in 1-MeA-induced oocyte maturation.
- * To identify changes in oocyte cortical proteins and TFP binding sites after trypsin treatment.
Main Methods:
- * Starfish oocytes were treated with 1-methyladenine (1-MeA) and trifluoperazine (TFP).
- * Oocytes were exposed to trypsin to assess changes in TFP sensitivity.
- * Protein composition of the oocyte cortex was analyzed, and TFP binding sites were localized using fluorescence microscopy.
Main Results:
- * Trypsin treatment for 10 minutes rendered starfish oocytes insensitive to TFP inhibition of maturation.
- * Trypsin did not affect the hormone-dependent period or 1-MeA concentration requirements.
- * Trypsin exposure altered the oocyte cortical protein profile, including the breakdown of a 140-kDa protein, and TFP binding localized to cortical granules.
Conclusions:
- * Trypsin-induced loss of TFP sensitivity suggests a role for trypsin-sensitive components in the oocyte cortex in TFP action.
- * Calmodulin and plasma membrane calmodulin-dependent enzymes are likely involved in mediating 1-MeA-induced oocyte maturation.
- * Changes in cortical proteins and TFP binding sites indicate a complex regulatory mechanism for oocyte maturation.