Phosphatidylinositol-4-phosphate 5-kinases (PIP5Ks, or PI4P5Ks) are a class of enzymes that

phosphorylate In chemistry, phosphorylation is the attachment of a phosphate group to a molecule or an ion. This process and its inverse, dephosphorylation, are common in biology and could be driven by natural selection. Text was copied from this source, ...

phosphatidylinositol 4-phosphate. They perform this reaction on the fifth

hydroxyl In chemistry, a hydroxy or hydroxyl group is a functional group with the chemical formula and composed of one oxygen atom covalently bonded to one hydrogen atom. In organic chemistry, alcohols and carboxylic acids contain one or more hydro ...

of the

myo-inositol Inositol, or more precisely ''myo''-inositol, is a carbocyclic sugar that is abundant in the brain and other mammalian tissues; it mediates cell signal transduction in response to a variety of hormones, neurotransmitters, and growth factors and ...

ring to form

phosphatidylinositol 4,5-bisphosphate Phosphatidylinositol 4,5-bisphosphate or PtdIns(4,5)''P''2, also known simply as PIP2 or PI(4,5)P2, is a minor phospholipid component of cell membranes. PtdIns(4,5)''P''2 is enriched at the plasma membrane where it is a substrate for a number o ...

Function

Phosphatidylinositol Phosphatidylinositol (or Inositol Phospholipid) consists of a family of lipids as illustrated on the right, where red is x, blue is y, and black is z, in the context of independent variation, a class of the phosphatidylglycerides. In such molecul ...

Phosphate In chemistry, a phosphate is an anion, salt, functional group or ester derived from a phosphoric acid. It most commonly means orthophosphate, a derivative of orthophosphoric acid . The phosphate or orthophosphate ion is derived from phosph ...

-5 kinase (PI4P5K) or PIP5K or PI5K family regulates diverse cellular processes such as

G protein-coupled receptor G protein-coupled receptors (GPCRs), also known as seven-(pass)-transmembrane domain receptors, 7TM receptors, heptahelical receptors, serpentine receptors, and G protein-linked receptors (GPLR), form a large group of evolutionarily-related p ...

(GPCR) signaling, vesicle trafficking, chemotaxis and cellular movement. There are at least two types of PIP5K found which includes Type I and Type II. Reinvestigation of the substrate specificity of PI(4)P5Ks, however, revealed that the type II PI(4)P5Ks catalyze phosphorylation of a novel phosphoinositide phosphati- dylinositol 5-phosphate at the D-4 position of the inositol ring, leading to the revised conclusion that the type II enzymes are actually phosphatidylinositol 5-phosphate 4-kinases. Thus, the PI(4)P5K family now comprises just the type I􏰂.Other types are also suspected in the nervous system but have not been well reported. These enzyme synthesize diverse Phosphatidyl Inositol 4,5 bisphosphate ( PI(4,5)P2 ) by phosphorylating the D- 5 position of the inositol ring of Phosphatidylinositol 4-phosphate]. PIP5KI is the most extensively studied and is synthesizing for most of the Phosphatidylinositol 4,5-bisphosphate, PI(4,5)P2 pool the cell. Type I phosphatidylinositol-4-phosphate 5-kinase (PIP5KI) are further classified as PIP5Kα, PIP5Kβ and PIP5Kγ on the basis of their basic differences in primary structure and the variation in the expression level in different compartment of cells, indicating that individual PIP5KI isoform has non identical function Moreover, PIP5Kγ, has three splicing variance; PIP5Kγ635, PIP5γ661, and PIP5Kγ687, making it one of the key regulators for producing PI(4,5)P2 that plays a role in diverse cellular processes. Although an extensive study to elucidate the role of PI(4,5)P2 and PIP5 kinase has been focused on many cellular processes such as vesicle trafficking, cell movement and cytoskeletal assembly, a very few studies have been reported for their role in neuronal development. PIP5K is highly expressed kinase in the nervous system of several organisms and plays important role in neuronal development including embryogenesis and post-natal neural development. The disruption of PIP5KIγ leads to broad developmental and cellular defects in mice indicating PIP5KIγ plays critical role for embryogenesis and adulthood of mice and its disruption causes fatality for postnatal life .html" ;"title="ref name=":2">">ref name=":2"> The embryo without PIP5KIγ has extensive prenatal lethality during embryonic development. The disruption of PIP5KIγ also causes neural tube closure defects caused by decreased PI(4,5)P2 level. In contrast to this, mice lacking PIPKIα or PIPKIβ have major impact during adulthood but no effect in prenatal embryo, Even in the absence of both PIPKIα and PIPKIβ, a single allele of PIPKIγ, can support normal the adulthood functioning, indicating PIPKIγ and PIPKIα have partially overlapping function during embryogenesis. In different experiments, the role of PIP5K in neurite outgrowth has been analyzed by knocking down PIP5Kα. The Nerve Growth Factor (NGF) induced neurite outgrowth was more obvious in knock down cells than in control cells. In contrary, the over-expression of PIP5Ka in to a PIP5Ka Knock down cells abrogated neurite outgrowth showing PIP5K acts as a negative regulator of NGF-induced neurite outgrowth through inhibiting the PI3K/ AKT signaling pathway in PC12 cells. A novel mechanism for the role of PIPKIα in regulating neuronal morphology by controlling microtubule dynamics is reported in mouse. During axon pathfinding, a growth cone is formed to guide the migrating

axon An axon (from Greek ἄξων ''áxōn'', axis), or nerve fiber (or nerve fibre: see spelling differences), is a long, slender projection of a nerve cell, or neuron, in vertebrates, that typically conducts electrical impulses known as action p ...

Growth cone A growth cone is a large actin-supported extension of a developing or regenerating neurite seeking its synaptic target. It is the growth cone that drives axon growth. Their existence was originally proposed by Spanish histologist Santiago Ram� ...

formation is induced by Kinesin Supar Family protein 2A (KIF2A) KIF2A- mediated depolymerization of microtubules. The interaction of PIPKα with KIF2A suppresses the elongation of axon branches. In association with Daam2, PIP5 kinase promotes

Wnt signaling The Wnt signaling pathways are a group of signal transduction pathways which begin with proteins that pass signals into a cell through cell surface receptors. The name Wnt is a portmanteau created from the names Wingless and Int-1. Wnt signaling ...

and receptor complex formation which is required for the regenerative myelination of the neuron. In the

central nervous system The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain and spinal cord. The CNS is so named because the brain integrates the received information and coordinates and influences the activity of all p ...

(CNS) of chick, PIP5K-PI(4,5)P2 mediated role of Daam2 has been reported for the development of neurons.

List of PIP4Ks

* Phosphatidylinositol-5-phosphate 4-kinase type-2 alpha (PIP4K2A) * Phosphatidylinositol-5-phosphate 4-kinase type-2 beta (PIP4K2B) * Phosphatidylinositol-5-phosphate 4-kinase type-2 gamma (PIP4K2C)

References

{{Reflist Phospholipids