Protein kinase C enzymes, regulates cell growth

Protein kinase C, commonly abbreviated to PKC (EC 2.7.11.13), is a family of protein kinase enzymes that are involved in controlling the function of other proteins through the phosphorylation of hydroxyl groups of serine and threonineamino acid residues on these proteins, or a member of this family. PKC enzymes in turn are activated by signals such as increases in the concentration of diacylglycerol (DAG) or calcium ions (Ca2+).[1] Hence PKC enzymes play important roles in several signal transduction cascades.[2]

The PKC family consists of fifteen isozymes in humans.[3] They are divided into three subfamilies, based on their second messenger requirements: conventional (or classical), novel, and atypical.[4] Conventional (c)PKCs contain the isoforms α, βI, βII, and γ. These require Ca2+, DAG, and a phospholipidsuch as phosphatidylserine for activation. Novel (n)PKCs include the δ, ε, η, and θ isoforms, and require DAG, but do not require Ca2+ for activation. Thus, conventional and novel PKCs are activated through the same signal transduction pathway as phospholipase C. On the other hand, atypical (a)PKCs (including protein kinase Mζ and ι / λ isoforms) require neither Ca2+ nor diacylglycerol for activation. The term “protein kinase C” usually refers to the entire family of isoforms.

Function

A multiplicity of functions have been ascribed to PKC. Recurring themes are that PKC is involved in receptor desensitization, in modulating membrane structure events, in regulating transcription, in mediating immune responses, in regulating cell growth, and in learning and memory. These functions are achieved by PKC-mediated phosphorylation of other proteins. However, the substrate proteins present for phosphorylation vary, since protein expression is different between different kinds of cells. Thus, effects of PKC are cell-type-specific:

Cell type Organ/system Activators
ligands –> GqGPCRs
Effects
smooth muscle cell (gastrointestinal tract sphincters) digestive system contraction
smooth muscle cells in:

Various contraction
smooth muscle cells in:

sensory system acetylcholine –> M3 receptor contraction
smooth muscle cell (vascular) circulatory system
smooth muscle cell (seminal tract)[9]:163[10] reproductive system ejaculation
smooth muscle cell (GI tract) digestive system
smooth muscle cell (bronchi) respiratory system bronchoconstriction[9]:187
proximal convoluted tubule cell kidney
  • stimulate NHE3 –> H+ secretion & Na+ reabsorption[14]
  • stimulate basolateral Na-K ATPase –> Na+ reabsorption[14]
neurons in autonomic ganglia nervous system acetylcholine –> M1 receptor EPSP
neurons in CNS nervous system
  • neuronal excitation (5-HT)[9]:187[15]
  • memory (glutamate)[16]
platelets circulatory system 5-HT –> 5-HT2A receptor[9]:187 aggregation[9]:187
ependymal cells (choroid plexus) ventricular system 5-HT –> 5-HT2C receptor[9]:187 cerebrospinal fluid secretion[9]:187
heart muscle circulatory system positive ionotropic effect[7]
serous cells (salivary gland) digestive system
serous cells (lacrimal gland) digestive system
  • ↑secretion[9]:127
adipocyte digestive system/endocrine system
hepatocyte digestive system
sweat gland cells integumentary system
  • ↑secretion[7]
parietal cells digestive system acetylcholine –> M3 receptors[17] gastric acid secretion

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connie dello buono

Health educator, author and enterpreneur motherhealth@gmail.com or conniedbuono@gmail.com ; cell 408-854-1883 Helping families in the bay area by providing compassionate and live-in caregivers for homebound bay area seniors. Blogs at www.clubalthea.com Currently writing a self help and self cure ebook to help transform others in their journey to wellness, Healing within, transform inside and out. This is a compilation of topics Connie answered at quora.com and posts in this site.

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