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J Rettig

Publications and source records attributed to J Rettig.

31 records · Page 2Linked to original sources
PubMed1996

Biochemical properties and subcellular distribution of the BI and rbA isoforms of alpha 1A subunits of brain calcium channels.

Biochemical properties and subcellular distribution of the class A calcium channel alpha 1 subunits (alpha 1A) from rat and rabbit brain were examined using site-directed anti-peptide antibodies specific for rat rbA (anti-CNA3) and for rabbit BI (anti-NBI-1 and anti-NBI-2) isoforms of alpha 1A. In immunoblotting experiments, anti-CNA3 specifically identifies multiple alpha 1A polypeptides with apparent molecular masses of 210, 190, and 160 kD, and anti-NBI-1 and anti-NBI-2 specifically recognize 190-kD alpha 1A polypeptides in rat brain membrane. In rabbit brain, anti-NBI-1 or anti-NBI-2 specifically detect alpha 1A polypeptides with apparent molecular masses of 220, 200, and 190 kD, while anti-CNA3 specifically recognizes 190-kD alpha 1A polypeptides. These polypeptides evidently represent multiple isoforms of alpha 1A present in both rat and rabbit brain. Anti-CNA3 specifically immunoprecipitates high affinity receptor sites for omega-conotoxin MVIIC (Kd approximately 100 pM), whereas anti-NBI-2 immunoprecipitates two distinct affinity receptor sites for omega-conotoxin MVIIC (Kd approximately 100 pM and approximately 1 microM). Coimmunoprecipitation experiments indicate that alpha 1A subunits recognized by anti-CNA3 and anti-NBI-2 are associated with syntaxin in a stable, SDS-resistant complex and with synaptotagmin. Immunofluorescence studies reveal that calcium channels recognized by anti-NBI-2 are localized predominantly in dendrites and nerve terminals forming synapses on them, while calcium channels recognized by anti-CNA3 are localized more prominently in cell bodies and in nerve terminals. The mossy fiber terminals in hippocampus and the terminals of climbing and parallel fibers in cerebellum are differentially stained by these isoform-specific antibodies. These results indicate that both rbA and BI isoforms of alpha 1A are expressed in rat and rabbit brain and form calcium channels having alpha 1A subunits with distinct molecular mass, pharmacology, and subcellular localization.

Amino Acid Sequence↗
PubMed1995

Molecular and functional characterization of a rat brain Kv beta 3 potassium channel subunit.

A novel potassium channel beta-subunit (Kv beta 3) was cloned from rat brain being the third member of a Kv beta subunit gene family. It is a protein of 403 amino acid residues with a 68% amino acid sequence homology to Kv beta 1.1. Kv beta 3 is primarily expressed in rat brain having a distribution distinct to those of Kv beta 1.1 and Kv beta 2. This subunit also has a long N-terminal structure and induces inactivation in N-terminal deleted Kv1.4 but not in other members of the Kv1 channel family. Similarly to Kv beta 1.1, the Kv beta 3-induced inactivation is regulated by the intracellular redox potential.

Amino Acid Sequence↗
PubMed1994

Inactivation properties of voltage-gated K+ channels altered by presence of beta-subunit.

Structural and functional diversity of voltage-gated Kv1-type potassium channels in rat brain is enhanced by the association of two different types of subunits, the membrane-bound, poreforming alpha-subunits and a peripheral beta-subunit. We have cloned a beta-subunit (Kv beta 1) that is specifically expressed in the rat nervous system. Association of Kv beta 1 with alpha-subunits confers rapid A-type inactivation on non-inactivating Kv1 channels (delayed rectifiers) in expression systems in vitro. This effect is mediated by an inactivating ball domain in the Kv beta 1 amino terminus.

Amino Acid Sequence↗
PubMed1994

Primary structure of a beta subunit of alpha-dendrotoxin-sensitive K+ channels from bovine brain.

Voltage-dependent cation channels are large heterooligomeric proteins. Heterologous expression of cDNAs encoding the alpha subunits alone of K+, Na+, or Ca2+ channels produces functional multimeric proteins; however, coexpression of those for the latter two with their auxiliary proteins causes dramatic changes in the resultant membrane currents. Fast-activating, voltage-sensitive K+ channels from brain contain four alpha and beta subunits, tightly associated in a 400-kDa complex; although molecular details of the alpha-subunit proteins have been determined, little is known about the beta-subunit constituent. Proteolytic fragments of a beta subunit from bovine alpha-dendrotoxin-sensitive neuronal K+ channels yielded nine different sequences. In the polymerase chain reaction, primers corresponding to two of these peptides amplified a 329-base-pair fragment in a lambda gt10 cDNA library from bovine brain; a full-length clone subsequently isolated encodes a protein of 367 amino acids (M(r) approximately 40,983). It shows no significant homology with any known protein. Unlike the channels' alpha subunits, the hydropathy profile of this sequence failed to reveal transmembrane domains. Several consensus phosphorylation motifs are apparent and, accordingly, the beta subunit could be phosphorylated in the intact K+ channels. These results, including the absence of a leader sequence and N-glycosylation, are consistent with the beta subunit being firmly associated on the inside of the membrane with alpha subunits, as speculated in a simplified model of these authentic K+ channels. Importantly, this first primary structure of a K(+)-channel beta subunit indicates that none of the cloned auxiliary proteins of voltage-dependent cation channels, unlike their alpha subunits, belong to a super-family of genes.

Amino Acid Sequence↗
PubMed1994

Identification of a syntaxin-binding site on N-type calcium channels.

Immunochemical studies have suggested a tight association of syntaxin with N-type calcium channels. Syntaxin specifically interacts with the fusion proteins containing the cytoplasmic loop (LII-III) between homologous repeats II and III of the alpha 1 subunit of the class B N-type calcium channel (alpha 1B) from rat brain, but not with those of the class A Q-type (alpha 1A) or the class S L-type (alpha 1S) calcium channels. This interaction is mediated by an 87 amino acid sequence (773-859) containing two overlapping predicted helix-loop-helix domains. The 87 amino acid peptide can specifically block binding of native N-type calcium channels to syntaxin, indicating that this binding site is required for stable interaction of these two proteins. Interaction takes place with the C-terminal one-third of syntaxin (residues 181-288), which is thought to be anchored in the presynaptic plasma membrane. Our results suggest a direct interaction between the cytoplasmic domains of these two presynaptic membrane proteins that could have an important role in the targeting and docking of synaptic vesicles near N-type calcium channels, enabling tight structural and functional association of calcium entry sites and neurotransmitter release sites.

Animals↗
PubMed1994

The inactivation behaviour of voltage-gated K-channels may be determined by association of alpha- and beta-subunits.

Voltage-gated K-channels of the Shaker related subfamily have two subunits, membrane integrated alpha- and peripheral beta-subunits. alpha-Subunits may assemble as tetramers and form in in vitro expression systems functional K-channels. beta-Subunits cannot from channels by themselves. Like for alpha-subunits, the rat nervous system apparently expresses a family of beta-subunit proteins. We have demonstrated that one rat K-channel beta-subunit, Kv beta 1, contains an inactivating domain. Upon association of alpha- and Kv beta 1-subunits, delayed-rectifier type K-channels are converted to rapidly inactivating A-type K-channels. The beta-subunit inactivation domain acts via a ball and chain type mechanism previously proposed for N-type inactivation of alpha-subunits. The association of alpha- and beta-subunits endows the nervous system with an unprecedented flexibility and diversity of K-channels which may play an important role in the regulation of nervous excitability.

Amino Acid Sequence↗
PubMed1992

Characterization of a Shaw-related potassium channel family in rat brain.

Previously, we characterized a Shaker-related family of voltage-gated potassium channels (RCK) in rat brain. Now, we describe a second family of voltage-gated potassium channels in the rat nervous system. This family is related to the Drosophila Shaw gene and has been dubbed Raw. In contrast to the RCK potassium channel family the Raw family utilizes extensive alternative splicing for expressing potassium channel subunits with variant C-termini. These alternative C-termini do not appear to influence the electrophysiological and pharmacological properties as studied in the Xenopus oocyte expression system. In situ hybridizations to sections of rat brain indicate that members of the Raw family are expressed in distinct areas of the central nervous system. Probably, Raw channels are expressed predominantly as homomultimers. Immunocytochemical experiments with antibodies against Raw3 and RCK4 proteins which form two distinct A-type potassium channels indicate that in hippocampus the two channels are expressed both in different neurons and in the same ones. In general, properties of Raw potassium channels appeared to be similar to RCK channels. However, Raw outward currents, in contrast to RCK currents, exhibit an intense rectification at test potentials higher than +20 to +40 mV. RCK and Raw channel subunits did not measurably coassemble into RCK/Raw heteromultimers after coinjecting RCK and Raw cRNA into Xenopus oocytes. These results suggest that members of the RCK and the Raw potassium channel families express potassium channels which form independent outward current systems. Combining the results of in situ hybridizations, immunocytochemical staining and expression of the cloned potassium channels in Xenopus oocytes demonstrates that unrestrained mixing of potassium channel subunits to form hybrid channels does not occur in the rat central nervous system. A single neuron is able to express multiple, independently assembled potassium channels.

Amino Acid Sequence↗
PubMed1991

Cloning and functional expression of a TEA-sensitive A-type potassium channel from rat brain.

A rat brain cDNA (Raw3) related to the Drosophila Shaw K+ channel family has been characterized. Raw3 cRNA leads to the formation of TEA-insensitive, fast inactivating (A-type) K+ channels when injected into Xenopus laevis oocytes. Raw3 channels have markedly different properties from the previously cloned rat A-type K+ channel RCK4, Raw3 channels operate in the positive voltage range.

Amino Acid Sequence↗
PubMed1989

[Korbinian Brodmann (1868-1918)].

Brodmann, an anatomically orientated neuropsychiatrist, is one of the most influential cortical localizationists. His comparative studies and brain maps are still fundamental for the descriptive anatomy of the cortex. Brodmann made his main contributions while working at the brain research institute of Oskar Vogt in Berlin (1901-1910). Due to unfavourable circumstances he was unable to extend his findings much further. We recount his biography on the basis of new source material, recently collected through a memorial archive in his hometown in south-west Germany. Modern methods have corroborated Brodmann's concept of cortical parcellation into "areae"--although their function is still largely unknown.

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