enzyme
Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products ...
that in humans is encoded by the ''MAP3K12''
gene
In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a b ...
.
Function
The protein encoded by this gene is a member of serine/threonine protein kinase family. This kinase contains a leucine-zipper domain, and is predominately expressed in neuronal cells. The phosphorylation state of this kinase in synaptic terminals was shown to be regulated by membrane depolarization via calcineurin. This kinase forms heterodimers with leucine zipper containing transcription factors, such as cAMP responsive element binding protein (CREB) and MYC, and thus may play a regulatory role in PKA or retinoic acid induced neuronal differentiation.
Interactions
MAP3K12 has been shown to
interact
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with
MAPK8IP1
C-jun-amino-terminal kinase-interacting protein 1 is an enzyme that in humans is encoded by the ''MAPK8IP1'' gene.
The protein encoded by this gene is a regulator of the pancreatic beta-cell function. It is highly similar to JIP-1, a mouse protein ...
,
MAP2K7
Dual specificity mitogen-activated protein kinase kinase 7, also known as MAP kinase kinase 7 or MKK7, is an enzyme that in humans is encoded by the ''MAP2K7'' gene. This protein is a member of the mitogen-activated protein kinase kinase family. ...
MAP3K12, otherwise known as DLK, can initiate coordinated signalling cascades that culminate in the phosphorylation of
C-Jun N-terminal kinases
c-Jun N-terminal kinases (JNKs), were originally identified as kinases that bind and phosphorylate c-Jun on Ser-63 and Ser-73 within its transcriptional activation domain. They belong to the mitogen-activated protein kinase family, and are res ...
or JNK. Several experiments have implicated this interaction as having a role in the developing mammalian nervous system. For example, neuronal migration and axon growth are critical components of neuronal development. DLK null mice have defects in neuronal migration,
hypoplasia
Hypoplasia (from Ancient Greek ὑπo- ''hypo-'' 'under' + πλάσις ''plasis'' 'formation'; adjective form ''hypoplastic'') is underdevelopment or incomplete development of a tissue or organ.cingulum and
internal capsule
The internal capsule is a white matter structure situated in the inferomedial part of each cerebral hemisphere of the brain. It carries information past the basal ganglia, separating the caudate nucleus and the thalamus from the putamen and the ...
. In addition, inhibition of DLK or JNK delays radial migration and disrupts the formation of the neocortex in mice. Another important function of the developing mammalian nervous system is neuronal
apoptosis
Apoptosis (from grc, ἀπόπτωσις, apóptōsis, 'falling off') is a form of programmed cell death that occurs in multicellular organisms. Biochemical events lead to characteristic cell changes ( morphology) and death. These changes in ...
. The absence of DLK also protects cultured mice sensory neurons from apoptosis that would normally be triggered by a lack of NGF. This, among other experiments, heavily implicates it as having a role in neuronal apoptosis.
DLK has several different interactions that contribute to mammalian nervous system development. For axon growth, DLK phosphorylates MAP2K4/7 which then phosphorylates JNK, activating it. In neuronal migration DLK phosphorylates MAP2K4/7 which phosphorylates JNK, and also interacts with JIP which then interacts with MAP2K4/7 and JNK. There is a similar interaction for neuronal apoptosis, where DLK phosphorylates JIP3 and MAP2K7, which both phosphorylate JNK. It is evident then that DLK interactions are a versatile and critical part of neuronal development in mammals.