Skip to content
Login Register

#intracellular calcium

2 public questions tagged with this topic.

Regeneration -ll

The cortical granule reaction requires an increase in intracellular:

Cortical granule exocytosis is strictly calcium-dependent exocytosis analogous to neurotransmitter release. Fertilization activates phospholipase C producing IP3 that triggers calcium release from endoplasmic reticulum via IP3 receptors. Cytoplasmic free calcium increases from nanomolar resting to micromolar levels propagating as wave across cortex. Calcium binds synaptotagmin-like calcium sensors on granule membranes promoting assembly of SNARE complexes driving membrane fusion and content discharge. Elevation of sodium, potassium, or magnesium accompanies fertilization potential but cannot substitute. Chelation of calcium by intracellular BAPTA injection completely abolishes cortical reaction demonstrating absolute requirement for intracellular calcium surge.

Ref: NCBI Bookshelf, Egg Activation: IP3-mediated calcium wave and cortical granule exocytosis in sea urchin.

View Details
Sea urchin -l

The cortical granule reaction requires an increase in intracellular:

Cortical granule exocytosis is triggered by calcium wave sweeping from sperm entry point across cortex. Phospholipase C zeta introduced by sperm hydrolyzes PIP2 generating IP3, which binds receptors on endoplasmic reticulum releasing stored Ca2+ into cytosol. Rising Ca2+ binds synaptotagmin and triggers SNARE-mediated fusion of cortical granules with plasma membrane. Calcium ionophore A23187 can artificially activate eggs mimicking envelope elevation. Sodium, potassium and magnesium fluctuations follow depolarization but essential fusogenic trigger is intracellular Ca2+ rise linking fertilization to polyspermy block and metabolic activation.

Ref: Whitaker, Physiol Rev 2006, Calcium wave in egg activation; Gilbert Chapter 7: Ca2+ dependent cortical reaction.

View Details