Dataset Information

Immunostaining for the ?3 isoform of the Na+/K+-ATPase is selective for functionally identified muscle spindle afferents in vivo.

ABSTRACT: Muscle spindle afferent (MSA) neurons can show rapid and sustained firing. Immunostaining for the ?3 isoform of the Na(+)/K(+)-ATPase (?3) in some large dorsal root ganglion (DRG) neurons and large intrafusal fibres suggested ?3 expression in MSAs (Dobretsov et al. 2003), but not whether ?3-immunoreactive DRG neuronal somata were exclusively MSAs. We found that neuronal somata with high ?3 immunointensity were neurofilament-rich, suggesting they have A-fibres; we therefore focussed on A-fibre neurons to determine the sensory properties of ?3-immunoreactive neurons. We examined ?3 immunointensity in 78 dye-injected DRG neurons whose conduction velocities and hindlimb sensory receptive fields were determined in vivo. A dense perimeter or ring of staining in a subpopulation of neurons was clearly overlying the soma membrane and not within satellite cells. Neurons with clear ?3 rings (n = 23) were all MSAs (types I and II); all MSAs had darkly stained ?3 rings, that tended to be darker in MSA1 than MSA2 units. Of 52 non-MSA A-fibre neurons including nociceptive and cutaneous low-threshold mechanoreceptive (LTM) neurons, 50 had no discernable ring, while 2 (A?/? cutaneous LTMs) had weakly stained rings. Three of three C-nociceptors had no rings. MSAs with strong ring immunostaining also showed the strongest cytoplasmic staining. These findings suggest that ?3 ring staining is a selective marker for MSAs. The ?3 isoform of the Na(+)/K(+)-ATPase has previously been shown to be activated by higher Na(+) levels and to have greater affinity for ATP than the ?1 isoform (in all DRG neurons). The high ?3 levels in MSAs may enable the greater dynamic firing range in MSAs.

SUBMITTER: Parekh A

PROVIDER: S-EPMC3002446 | biostudies-literature | 2010 Nov

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Immunostaining for the α3 isoform of the Na+/K+-ATPase is selective for functionally identified muscle spindle afferents in vivo.

Parekh A A Campbell A J M AJ Djouhri L L Fang X X McMullan S S Berry C C Acosta C C Lawson S N SN

The Journal of physiology 20100831 Pt 21

Muscle spindle afferent (MSA) neurons can show rapid and sustained firing. Immunostaining for the α3 isoform of the Na(+)/K(+)-ATPase (α3) in some large dorsal root ganglion (DRG) neurons and large intrafusal fibres suggested α3 expression in MSAs (Dobretsov et al. 2003), but not whether α3-immunoreactive DRG neuronal somata were exclusively MSAs. We found that neuronal somata with high α3 immunointensity were neurofilament-rich, suggesting they have A-fibres; we therefore focussed on A-fibre ne ...[more]

PMID: 20807787

Similar Datasets

Project description:Na⁺/K⁺-ATPase maintains electrochemical gradients of Na⁺ and K⁺ essential for a variety of cellular functions including neuronal activity. The α-subunit of the Na⁺/K⁺-ATPase exists in four different isoforms (α1-α4) encoded by different genes. With a view to future use of pig as an animal model in studies of human diseases caused by Na⁺/K⁺-ATPase mutations, we have determined the porcine coding sequences of the α1-α3 genes, ATP1A1, ATP1A2, and ATP1A3, their chromosomal localization, and expression patterns. Our ATP1A1 sequence accords with the sequences from several species at five positions where the amino acid residue of the previously published porcine ATP1A1 sequence differs. These corrections include replacement of glutamine 841 with arginine. Analysis of the functional consequences of substitution of the arginine revealed its importance for Na⁺ binding, which can be explained by interaction of the arginine with the C-terminus, stabilizing one of the Na⁺ sites. Quantitative real-time PCR expression analyses of porcine ATP1A1, ATP1A2, and ATP1A3 mRNA showed that all three transcripts are expressed in the embryonic brain as early as 60 days of gestation. Expression of α3 is confined to neuronal tissue. Generally, the expression patterns of ATP1A1, ATP1A2, and ATP1A3 transcripts were found similar to their human counterparts, except for lack of α3 expression in porcine heart. These expression patterns were confirmed at the protein level. We also report the sequence of the porcine ATP1A3 promoter, which was found to be closely homologous to its human counterpart. The function and specificity of the porcine ATP1A3 promoter was analyzed in transgenic zebrafish, demonstrating that it is active and drives expression in embryonic brain and spinal cord. The results of the present study provide a sound basis for employing the ATP1A3 promoter in attempts to generate transgenic porcine models of neurological diseases caused by ATP1A3 mutations.

Project description:The transmembrane Na(+)-/K(+) ATPase is located at the plasma membrane of all mammalian cells. The Na(+)-/K(+) ATPase utilizes energy from ATP hydrolysis to extrude three Na(+) cations and import two K(+) cations into the cell. The minimum constellation for an active Na(+)-/K(+) ATPase is one alpha (α) and one beta (β) subunit. Mammals express four α isoforms (α1-4), encoded by the ATP1A1-4 genes, respectively. The α1 isoform is ubiquitously expressed in the adult central nervous system (CNS) whereas α2 primarily is expressed in astrocytes and α3 in neurons. Na(+) and K(+) are the principal ions involved in action potential propagation during neuronal depolarization. The α1 and α3 Na(+)-/K(+) ATPases are therefore prime candidates for restoring neuronal membrane potential after depolarization and for maintaining neuronal excitability. The α3 isoform has approximately four-fold lower Na(+) affinity compared to α1 and is specifically required for rapid restoration of large transient increases in [Na(+)]i. Conditions associated with α3 deficiency are therefore likely aggravated by suprathreshold neuronal activity. The α3 isoform been suggested to support re-uptake of neurotransmitters. These processes are required for normal brain activity, and in fact autosomal dominant de novo mutations in ATP1A3 encoding the α3 isoform has been found to cause the three neurological diseases Rapid Onset Dystonia Parkinsonism (RDP), Alternating Hemiplegia of Childhood (AHC), and Cerebellar ataxia, areflexia, pes cavus, optic atrophy, and sensorineural hearing loss (CAPOS). All three diseases cause acute onset of neurological symptoms, but the predominant neurological manifestations differ with particularly early onset of hemiplegic/dystonic episodes and mental decline in AHC, ataxic encephalopathy and impairment of vision and hearing in CAPOS syndrome and late onset of dystonia/parkinsonism in RDP. Several mouse models have been generated to study the in vivo consequences of Atp1a3 modulation. The different mice show varying degrees of hyperactivity, gait problems, and learning disability as well as stress-induced seizures. With the advent of several Atp1a3-gene or chemically modified animal models that closely phenocopy many aspects of the human disorders, we will be able to reach a much better understanding of the etiology of RDP, AHC, and CAPOS syndrome.

Dataset Information

Immunostaining for the ?3 isoform of the Na+/K+-ATPase is selective for functionally identified muscle spindle afferents in vivo.

Publications

Immunostaining for the α3 isoform of the Na+/K+-ATPase is selective for functionally identified muscle spindle afferents in vivo.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure