Distribution of neuronal KCC2a and KCC2b isoforms in mouse CNS

Abstract

The neuronal K-Cl cotransporter KCC2 maintains the low intracellular chloride concentration required for the fast hyperpolarizing actions of inhibitory neurotransmitters in mature central nervous system (CNS). The KCC2 gene produces two isoforms, KCC2a and KCC2b, that differ in their N-termini. Increase of KCC2b in the cortex underlies the developmental shift in γ-aminobutyric acid (GABA)ergic responses, whereas the physiological role of KCC2a is still poorly characterized. The two KCC2 isoforms show equal distribution in mouse brainstem neurons at birth; however their postnatal expression patterns, and the subcellular localization of KCC2a, have not yet been described. Here, we compared the pattern of KCC2a and KCC2b expression in different regions of postnatal mouse CNS by immunohistochemistry by using isoform-specific antibodies. Tissue from KCC2a isoform-specific knockout mice was used as a negative control. KCC2b expression increased postnatally and was widely expressed in adult brain. KCC2a immunoreactivity was low or absent in most parts of the adult cortex, hippocampus, thalamus, and cerebellar cortex. Both isoforms were widely present in the developing and mature hypothalamus, a large part of the brainstem, and the spinal cord. A notable exception was the lack of KCC2a staining in the brainstem auditory system. At the subcellular level, the isoforms were only partially colocalized. In neuronal somas, KCC2b immunoreactivity was concentrated at the plasma membrane, whereas KCC2a signal was not. Moreover, although both isoforms were expressed in microtubule-associated protein (MAP)2-positive dendrites, they appeared in non-overlapping dendritic compartments. The results, together with those of previous studies, suggest that KCC2a and KCC2b have overlapping roles in neonatal neurons but presumably different roles in mature neurons.

Expressions of ion co-transporter genes in salicylate-induced tinnitus and treatment effects of spirulina

“…K-Cl co-transporter KCC3 may be involved in degenerative peripheral neuropathies [19]. The neuronal KCC2 maintains the low intracellular chloride concentration required for the fast hyperpolarizing actions of inhibitory neurotransmitters in the mature central nervous system (CNS) [10, 17]. We found that salicylate could increase the mRNA expression of KCC2.…”

“…Among them, KCC2 is a neuron-specific Cl − transporter whose role in adult central nervous neurons is to maintain low intracellular Cl − concentrations needed for the hyperpolarizing responses to the inhibitory amino acid GABA and glycine of the auditory nucleus [10, 17]. The NKCC is a class of membrane proteins that transport Na, K, and Cl ions into and out of a wide variety of epithelial and non-epithelial cells.…”

A Novel View on the Role of Intracellular Tails in Surface Delivery of the Potassium-Chloride Cotransporter KCC2

“…The mammalian KCC2 gene (aka Slc12a5 ) generates two major isoforms, KCC2a and KCC2b, that differ in their N termini (Uvarov et al, 2007) and their developmental and spatial profile of expression (Markkanen et al, 2014). Historically, the first KCC2 molecule, discovered by Payne et al in 1996, was actually the isoform KCC2b; these days, it is considered the major and most important isoform in the adult brain and spinal cord (Payne et al, 1996; Rivera et al, 1999; Stein et al, 2004; Markkanen et al, 2014).…”

“…Historically, the first KCC2 molecule, discovered by Payne et al in 1996, was actually the isoform KCC2b; these days, it is considered the major and most important isoform in the adult brain and spinal cord (Payne et al, 1996; Rivera et al, 1999; Stein et al, 2004; Markkanen et al, 2014). Mice with knocked out KCC2b are characterized by increased epileptiform-like neuronal network activity and die at juvenile age of 2–3 postnatal weeks (Woo et al, 2002).…”

“…Mice with knocked out KCC2b are characterized by increased epileptiform-like neuronal network activity and die at juvenile age of 2–3 postnatal weeks (Woo et al, 2002). The KCC2a isoform is expressed in immature neurons of all brain regions but is absent or expressed at a low level in mature cortex, hippocampus, thalamus, and cerebellar cortex (Uvarov et al, 2007; Markkanen et al, 2014). Mice with knocked out KCC2a appear grossly normal, although their phenotype has not been characterized in detail (Markkanen et al, 2014).…”