A wide range of Ca2+ signaling pathways deliver the spatial and temporal Ca2+ signals necessary to control the specific functions of different cell types, via various effector proteins and protein kinases

1. Calcium Signaling
{Calcium Calmodulin Cascade}
Dr. Vibha Khanna
Associate prof.
Botany

2. Spatial and Temporal Dynamics of Calcium ions
• A wide range of Ca2+ signaling pathways deliver the spatial and temporal
Ca2+ signals necessary to control the specific functions of different cell
types.
• The release of Ca2+ by InsP3 (inositol 1,4,5-trisphosphate) plays a central
role in many of these signaling pathways.
• Their resulting influence on transcriptional processes (gene expression)
maintain the integrity and stability of these cell-specific signaling pathways.

3. Calcium Signature
• Different stimuli can elicit distinct Ca2+ signals, also referred to as
Ca2+ signatures.
• Patterns of Ca2+ signatures may differ in the amplitude, duration,
localization and frequency of Ca2+ oscillations, and there is evidence that
these parameters are used to encode the information required to initiate
specific and appropriate responses for a given stimulus
• Ca2+ signals in the nucleus or the cytosol can result in specific changes in
gene expression

5. Process and Regulation of Calcium Signaling
Pathway
• G protein-coupled receptor (GPCR) activates
phospholipase C β (PLC β) and RTK activates PLC γ
which in turn, cleave phosphatidylinositol 4, 5
bisphosphate (PIP2) into 1, 4, 5-inositol
trisphosphate (IP3) and diacylglycerol (DAG).
• Ca2+ binds to the C2 domain of PKCα, β1, β2, and γ
subtypes initiate translocation to the membrane,
where coincident DAG binding activates Protein
kinase C (PKC).
• Ca2+ binding to the C2 domain of PKC α, β1, β2, and
γ subtypes initiates translocation to the membrane,
where coincident DAG binding activates it.
• Ca2+-sensitive DAG kinase phosphorylates DAG to
produce phosphatidic acid, while DAG lipase
converts DAG to arachidonic acid, thus to generate
a host of bioreactive molecules.
• Thus, “Ca2+ signaling,” amplifies the signal by
activating a range of pathways in the cell

6. Calcium signaling and Protein Kinases
• CDPK is a class of plant protein kinases that contain a kinase domain
and a Ca2+-binding domain bearing 4 EF-hands.
• Ca2+/CaM dependent kinase (CCaMK)
• CCaMK has a C-terminal regulatory domain, a Ca2+ binding domain
consisting of 3 EF-hands, and it can be activated by CaM.
• Other Ca2+-binding proteins including CaM and CBL lack an effector
domain such as the kinase domain of CDPK and CCaMK.

7. • CBL and CaM are small proteins with three and four EF-hand motifs
respectively, which function as sensor relays via Ca2+-dependent interaction
with effector proteins.
• CBL belongs to a family of plant proteins related to the regulatory B subunit
of calcineurin.
• To transmit Ca2+ signals, CBLs interact with a family of protein kinases
similar to the SNF-protein kinase from yeast, and modulate their kinase
activity
• CaM was identified in plants and animals more than two decades ago and
named calmodulin for CALcium MODULating proteIN.
• A large repertoire of CaM target proteins with diverse cellular functions is
found in plants, indicating that CaM regulates a wide variety of cellular
events.

8. The calmodulin (CaM) family is a major class of calcium sensor proteins which collectively play a
crucial role in cellular signaling cascades through the regulation of numerous target proteins.