Intracellular Signaling Mechanisms

Second messengers initiate and coordinate intracellular signaling pathways following receptor activation.

Calcium ions control various cellular processes, including gene transcription, muscle contraction, and cell proliferation.

Key components include Ca2+ pumps such as SERCA, buffered by reticuloplasmins like calsequestrin.

<p>Phospholipase C hydrolyzes PtdIns(4,5)P2 to generate second messengers DAG and IP3, which are crucial for calcium signaling.</p> Signup and view all the answers

<p>The two second messengers are diacylglycerol (DAG) and inositol-1,4,5-trisphosphate (IP3), which play roles in activating protein kinase C and releasing calcium from the ER, respectively.</p> Signup and view all the answers

<p>IP3 induces calcium release from the endoplasmic reticulum.</p> Signup and view all the answers

<p>DAG activates protein kinase C (PKC).</p> Signup and view all the answers

<p>The IP3R is a tetramer with a cytoplasmic N-terminal domain, a C-terminal channel domain, and a regulatory domain.</p> Signup and view all the answers

<p>Calcium can both activate and inhibit the IP3 receptors through a biphasic regulation mechanism.</p> Signup and view all the answers

<p>Blips are small local releases of calcium, spikes are repetitive localized increases, puffs are larger releases leading to more widespread effects, and waves are global calcium increases that propagate through the cell.</p> Signup and view all the answers

<p>IP3 is produced through the breakdown of phosphatidylinositol 4,5-bisphosphate (PIP2).</p> Signup and view all the answers

<p>Higher stimulation leads to increased calcium release and the activation of more IP3 receptors, resulting in puffs of calcium.</p> Signup and view all the answers

<p>The diffusion coefficient of IP3 is 268 μm²/s, indicating that it is highly mobile within the cytoplasm.</p> Signup and view all the answers

<p>Fluo-4 was used and it was excited at 488nm.</p> Signup and view all the answers

<p>The frequency of Ca2+ spikes indicates the concentration of the stimulus, while the shape conveys the identity of the agonist.</p> Signup and view all the answers

<p>Calcium triggers egg activation and facilitates the fertilization process.</p> Signup and view all the answers

<p>Capacitation involves cholesterol efflux, increased PM permeability, and influx of Ca2+ and HCO3-.</p> Signup and view all the answers

<p>The primary outcome is hyperactive motility in sperm.</p> Signup and view all the answers

<p>Calmodulin dependent kinase forms as a result of calcium binding to calmodulin.</p> Signup and view all the answers

<p>Adenylyl cyclase and Protein Kinase A (PKA) are activated.</p> Signup and view all the answers

<p>The fertilizing sperm also bestows centrioles and a trigger for egg activation.</p> Signup and view all the answers

<p>Absence of functional PLCζ does not compromise spermatogenesis and sperm quality parameters such as viability, motility, hyperactivity, and ability to undergo the acrosome reaction.</p> Signup and view all the answers

<p>Some eggs can develop, albeit at greatly reduced efficiency and after a significant time-delay.</p> Signup and view all the answers

<p>Ca2+ oscillations trigger the exit of meiosis and initiate mitosis, facilitating subsequent embryo development.</p> Signup and view all the answers

<p>The cortical reaction involves the release of enzymes like Ovastacin that impair further penetration by sperm, thus preventing polyspermy.</p> Signup and view all the answers

<p>MPF is composed of Cdk1 and Cyclin B, and it regulates meiosis by triggering chromatin condensation and the formation of the meiotic spindle.</p> Signup and view all the answers

<p>MPF phosphorylates the three lamins in the nuclear lamina, leading to the breakdown of the nuclear envelope into small vesicles.</p> Signup and view all the answers

<p>PLCζ acts as the physiological trigger for Ca2+ oscillations in eggs, which are necessary for fertilization and subsequent developmental processes.</p> Signup and view all the answers

<p>The mechanisms are the fast block to polyspermy, which is a depolarization of the oolemma, and the slow block to polyspermy, which involves the cortical reaction.</p> Signup and view all the answers

<p>Ca2+ oscillations trigger the exit of meiosis and initiate mitosis.</p> Signup and view all the answers

<p>EMI2 (early mitotic inhibitor 2).</p> Signup and view all the answers

<p>APC/C, or anaphase-promoting complex, is involved in regulating the transition from metaphase to anaphase.</p> Signup and view all the answers

<p>CaMKII (Ca2+/calmodulin-dependent protein kinase II).</p> Signup and view all the answers

<p>Securin prevents the separation of sister chromatids by inhibiting separase until anaphase.</p> Signup and view all the answers

<p>Polo-like kinase 1 is involved in regulating various processes during mitosis, including checkpoint control.</p> Signup and view all the answers

<p>The SCF complex mediates the ubiquitination of specific proteins to regulate their degradation.</p> Signup and view all the answers

<p>Elevated Ca2+ levels activate pathways that drive the transition into mitosis.</p> Signup and view all the answers

<p>CaMKII activates the anaphase-promoting complex (APC), which leads to the degradation of securin.</p> Signup and view all the answers

<p>Increased levels of Ca2+ trigger the activation of CaMKII, which in turn activates the APC.</p> Signup and view all the answers

<p>Securin degradation is necessary to allow for chromosomal segregation during meiotic anaphase I.</p> Signup and view all the answers

<p>SCF ubiquitin ligase targets specific proteins for degradation, thereby regulating cell cycle progression.</p> Signup and view all the answers

<p>Experiments demonstrated that introducing recombinant PLCζ led to effective blastocyst formation in oocytes with dysfunctional PLCζ.</p> Signup and view all the answers

<p>Immunocytochemistry helps identify the presence or absence of key proteins like PLCζ in spermatozoa, which can affect fertility.</p> Signup and view all the answers

<p>Polo-like kinase 1 is involved in various cell cycle processes, particularly in mitosis and meiosis.</p> Signup and view all the answers

<p>PLCζ can be localized differently, showing absence in globozoospermic men and different patterns in non-globozoospermic patients.</p> Signup and view all the answers