KCNE5
KCNE5
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KCNE5

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KCNE5

KCNE1-like also known as KCNE1L is a protein that in humans is encoded by the KCNE1L gene.

Voltage-gated potassium (Kv) channels represent the most complex class of voltage-gated ion channels from both functional and structural standpoints. Their diverse functions include regulating neurotransmitter release, heart rate, insulin secretion, neuronal excitability, epithelial electrolyte transport, smooth muscle contraction, and cell volume. KCNE5 encodes a membrane protein, KCNE5 (originally named KCNE1-L) that has sequence similarity to the KCNE1 gene product, a member of the potassium channel, voltage-gated, isk-related subfamily.

The KCNE gene family comprises five genes in the human genome, each encoding a type I membrane protein. The KCNE subunits are potassium channel regulatory subunits that do not pass currents themselves but alter the properties of potassium channel pore-forming alpha subunits. KCNE5 is thus far the least-studied member of the KCNE family, but it is known to regulate a number of different Kv channel subtypes. KCNE5 co-assembles with KCNQ1, a Kv alpha subunit best known for its role in ventricular repolarization and in multiple epithelia. This co-assembly induces a +140 mV shift in voltage dependence of activation (when co-expressed in CHO cells) which would inhibit KCNQ1 activity across the normal physiological voltage range in most tissues.

KCNE5 also inhibits activity of channels formed with KCNQ1 and KCNE1. While reportedly not affecting KCNQ2, KCNQ2/3 or KCNQ5 channel activity, KCNE5 inhibits KCNQ4 in CHO cells but not in oocytes.

Although it has no known effects on hERG (Kv11.1) or Kv1.x family channel activity, KCNE5 inhibits Kv2.1 activity 50% and accelerates activation, slows deactivation and accelerates the recovery from closed state inactivation of channels formed by Kv2.1 and the 'silent' alpha subunit, Kv6.4.

KCNE5 was previously reported to not regulate Kv4.2 or Kv4.3, but has been found to accelerate, and left-shift the voltage dependence of, inactivation of Kv4.3-KChIP2 channel complexes.

The KCNE family subunits are type I membrane proteins with an extracellular N-terminus and intracellular C-terminus. The transmembrane domain is alpha helical in KCNE1, 2 and 3 and predicted to also be helical in KCNE4 and KCNE5. The acknowledged role of members of the KCNE family is as Kv channel beta subunits, regulating the functional properties of Kv alpha subunits, with all three segments of the beta subunit contributing to binding, functional modulation and/or trafficking modulation to a greater or lesser degree. The high resolution structure of KCNE5 has not yet been determined, as of 2016. KCNE5 is an X-linked gene encoding a 143 residue protein in Homo sapiens.

Human KCNE5 transcripts are most highly expressed in cardiac and skeletal muscle, spinal cord and brain, and it is also detectable in placenta. In mice, Kcne5 transcript was detected in embryonic cranial nerve migrating crest cells, ganglia, somites and myoepicaridal layer.

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