Podcast
Questions and Answers
Which protein is classified as a calcium binding protein with an EF-hand motif?
Which protein is classified as a calcium binding protein with an EF-hand motif?
What is the primary function of Ca2+-ATPases in muscle contraction?
What is the primary function of Ca2+-ATPases in muscle contraction?
Calcium can enter cells through which of the following mechanisms?
Calcium can enter cells through which of the following mechanisms?
Which of these statements correctly describes the function of the plasma membrane Ca2+ ATPase (PMCA)?
Which of these statements correctly describes the function of the plasma membrane Ca2+ ATPase (PMCA)?
Signup and view all the answers
Which of the following is NOT a type of calcium transporter mentioned?
Which of the following is NOT a type of calcium transporter mentioned?
Signup and view all the answers
Which type of calcium ATPase is responsible for transporting calcium in the sarcoplasmic reticulum?
Which type of calcium ATPase is responsible for transporting calcium in the sarcoplasmic reticulum?
Signup and view all the answers
What is the typical 'free' intracellular concentration of calcium ions [Ca2+i] in cells?
What is the typical 'free' intracellular concentration of calcium ions [Ca2+i] in cells?
Signup and view all the answers
Which protein is NOT part of the calcium signaling proteins but rather acts as a calcium binding protein?
Which protein is NOT part of the calcium signaling proteins but rather acts as a calcium binding protein?
Signup and view all the answers
What role do Na+/Ca2+ exchangers like NCX1, NCX2, and NCX3 play in cellular function?
What role do Na+/Ca2+ exchangers like NCX1, NCX2, and NCX3 play in cellular function?
Signup and view all the answers
What is the primary characteristic of calcium buffering proteins such as Calnexin and Calsquestrin?
What is the primary characteristic of calcium buffering proteins such as Calnexin and Calsquestrin?
Signup and view all the answers
What is the primary function of PMCA in calcium signaling?
What is the primary function of PMCA in calcium signaling?
Signup and view all the answers
Which protein regulates the activity of the SERCA pump?
Which protein regulates the activity of the SERCA pump?
Signup and view all the answers
Which of the following correctly describes NCX function?
Which of the following correctly describes NCX function?
Signup and view all the answers
What role does the α1 subunit play in voltage-gated calcium channels?
What role does the α1 subunit play in voltage-gated calcium channels?
Signup and view all the answers
How many splice variants are produced by the four ATP2B genes encoding PMCA?
How many splice variants are produced by the four ATP2B genes encoding PMCA?
Signup and view all the answers
Which calcium channel type is primarily associated with pacemaker activity in the heart?
Which calcium channel type is primarily associated with pacemaker activity in the heart?
Signup and view all the answers
What is the main consequence of binding calmodulin to PMCA?
What is the main consequence of binding calmodulin to PMCA?
Signup and view all the answers
What activates inositol 1,4,5-trisphosphate receptors (IP3R) in calcium signaling?
What activates inositol 1,4,5-trisphosphate receptors (IP3R) in calcium signaling?
Signup and view all the answers
Which calcium transport mechanism is primarily responsible for calcium release from intracellular stores?
Which calcium transport mechanism is primarily responsible for calcium release from intracellular stores?
Signup and view all the answers
Which of the following statements is true regarding the efficiency of calcium transport by SERCA?
Which of the following statements is true regarding the efficiency of calcium transport by SERCA?
Signup and view all the answers
What is a primary function of Ca2+ -ATPases in cells?
What is a primary function of Ca2+ -ATPases in cells?
Signup and view all the answers
Which of the following statements accurately describes Na+/Ca2+ exchangers?
Which of the following statements accurately describes Na+/Ca2+ exchangers?
Signup and view all the answers
What role do STIM and Orai receptors play in cellular calcium signaling?
What role do STIM and Orai receptors play in cellular calcium signaling?
Signup and view all the answers
Which process is primarily driven by the signaling molecule IP3?
Which process is primarily driven by the signaling molecule IP3?
Signup and view all the answers
In cellular processes, how does calcium function in exocytosis?
In cellular processes, how does calcium function in exocytosis?
Signup and view all the answers
What is a key characteristic of voltage-gated calcium channels?
What is a key characteristic of voltage-gated calcium channels?
Signup and view all the answers
Which of the following best describes the functions of calcium binding proteins?
Which of the following best describes the functions of calcium binding proteins?
Signup and view all the answers
Which cellular function is NOT directly influenced by calcium signaling?
Which cellular function is NOT directly influenced by calcium signaling?
Signup and view all the answers
How does calcium contribute to long-term potentiation?
How does calcium contribute to long-term potentiation?
Signup and view all the answers
What effect does calcium have on apoptotic processes?
What effect does calcium have on apoptotic processes?
Signup and view all the answers
What is the role of STIM1 in store-operated calcium entry?
What is the role of STIM1 in store-operated calcium entry?
Signup and view all the answers
Which of the following proteins are essential for facilitating store-operated calcium entry?
Which of the following proteins are essential for facilitating store-operated calcium entry?
Signup and view all the answers
How do calcium-binding proteins primarily function in cells?
How do calcium-binding proteins primarily function in cells?
Signup and view all the answers
What happens to STIM1 upon calcium store-depletion?
What happens to STIM1 upon calcium store-depletion?
Signup and view all the answers
Which transport mechanism is primarily responsible for calcium egress from the sarcoplasmic reticulum?
Which transport mechanism is primarily responsible for calcium egress from the sarcoplasmic reticulum?
Signup and view all the answers
What effect do gain-of-function mutations in STIM1 have on calcium signaling?
What effect do gain-of-function mutations in STIM1 have on calcium signaling?
Signup and view all the answers
Which type of calcium channel is involved in voltage-dependent calcium entry?
Which type of calcium channel is involved in voltage-dependent calcium entry?
Signup and view all the answers
What primarily limits the sustained increase in cytosolic Ca2+ when relying solely on intracellular stores?
What primarily limits the sustained increase in cytosolic Ca2+ when relying solely on intracellular stores?
Signup and view all the answers
What would be the consequence of a malfunctioning Na+/Ca2+ exchanger (NCX) in a cell?
What would be the consequence of a malfunctioning Na+/Ca2+ exchanger (NCX) in a cell?
Signup and view all the answers
Which proteins are primarily responsible for the transport of calcium ions back into the endoplasmic reticulum?
Which proteins are primarily responsible for the transport of calcium ions back into the endoplasmic reticulum?
Signup and view all the answers
Study Notes
Calcium Homeostasis - Part 2
- Calcium homeostasis occurs both extracellularly and intracellularly.
- Intracellular calcium is primarily bound by calcium-binding proteins or calcium-buffering proteins within the cytoplasm and cellular organelles like the sarcoplasmic reticulum.
Calcium Entry & Egress
- Calcium moves into and out of cells and organelles through a variety of proteins:
- Ca2+ ATPases:
- ATP2B (plasma membrane), ATP2A (endoplasmic/sarcoplasmic reticulum) and ATP2C (golgi).
- Voltage-gated Calcium channels, specifically L-type calcium channels
- Na+/Ca2+ exchanger (NCX1, NCX2, NCX3)
- Permeability transition pore
Calcium Binding Proteins
-
EF-hand motif containing proteins:
- Calmodulin
- S100 proteins
- Calcineurin
-
C2-domain containing proteins:
- Protein kinase C (PKC)
- Phospholipase-A (PLA)
- Phospholipase-C (PLC)
-
Calcium buffering proteins:
- Calnexin: 25 calcium binding sites located in the endoplasmic reticulum
- Calsquestrin: 70 calcium binding sites located in the sarcoplasmic reticulum
Intracellular Calcium Signaling
- Intracellular calcium plays a role in:
- Neurotransmitter and hormone release
- Muscle contraction
- Cell excitability
- Calcium-dependent conductance
- Synaptic plasticity
- Long-term potentiation
- Apoptosis
- Ischemic brain damage
- Cytoskeletal changes
- Neurite outgrowth
- Protein synthesis
Importance of Calcium
- Cellular functions reflect unique intrinsic features of calcium, such as its ionic radius and divalent charge.
- These features allow for discriminating mechanisms for cellular calcium concentration regulation.
- Specific calcium transporters ensure precise regulation of cellular calcium concentrations.
Vitamin D Metabolites & NCX
- NCX belongs to the Ca2+/cation antiporter superfamily.
- responsible for moving Ca2+ out of the cell.
- The activity of this exchanger can be modulated by Na+ and Ca2+ binding domains.
- It's encoded by the SLC8 gene, producing three isoforms: NCX1 (ubiquitous), NCX2 & NCX3 (brain and skeletal muscle)
Voltage-gated Ca2+ Channels (VGCC/VOC)
- VGCCs have an alpha (α1) subunit, which contains ion selectivity and the voltage sensor.
- They have intracellular subunits like beta (β) and extracellular subunits like alpha-2-delta (α2δ), which affect channel trafficking and regulation.
- VGCCs are encoded by CACNA1 genes.
- Three subgroups of VGCCs are L-type (skeletal, smooth, cardiac muscle, secretory tissues and nervous system), P/Q-type, N-type and R-type (nervous system) and T-type (neurons and the heart, pacemaker activity).
Inositol 1,4,5-trisphosphate (IP3)
- Ca2+ release from intracellular stores (like the endoplasmic reticulum (ER)) is dependent on inositol 1,4,5-trisphosphate receptors (IP3R).
- IP3R are tetramers of 4 transmembrane spanning helices
- Phospholipase C (PLC) cleaves PIP2 into IP3 and DAG.
Store-Operated Calcium Entry (SOCE)
- SOCE is the process by which Ca2+ enters cells when intracellular Ca2+ stores are depleted.
- This is facilitated by the proteins STIM1 and Orai.
- STIM proteins sense changes in the luminal Ca2+ concentration in intracellular stores
- When these stores deplete, STIM proteins oligomerise and move to the ER/SR-PM. This process attracts Orai proteins.
- Orai channels then open in the membrane and allow Ca2+ influx.
SOCE Mutations
- Mutations in STIM1 have been observed where a gain of function occurs, which increases the SOCE.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
