Contrasting subcellular localization of the Kv1.2 K+ channel subunit in different neurons of rat brain

Abstract

In the nervous system, a wide diversity of K+ channels are formed by the oligomeric assembly of subunits encoded by a large number of K+ channel genes. The physiological functions of a specific K+ channel subunit in vivo will be dictated in part by its subcellular location within neurons. We have used a combined in situ hybridization and immunocytochemical approach to determine the subcellular distribution of Kv1.2, a member of the Shaker subfamily of K+ channel genes. In contrast to other characterized K+ channel subunits, Kv1.2 protein shows a complex differential subcellular distribution in neurons of rat brain. In some of these neurons (e.g., hippocampal and cortical pyramidal cells, and Purkinje cells), Kv1.2 is concentrated in dendrites, while in others (e.g., cerebellar basket cells), Kv 1.2 is predominantly, if not exclusively, localized to nerve terminals. Furthermore, Kv1.2 immunoreactivity was also detected in certain axon tracts. We hypothesize that the differential sorting of Kv1.2 could result from association of Kv1.2 with varying heterologous K+ channel subunits in different cell types, with the implication that Kv1.2 may participate in distinct heteromultimeric K+ channels in different subcellular domains. The findings suggest that Kv1.2-containing K+ channels may play diverse functional roles in several neuronal compartments, regulating presynaptic or postsynaptic membrane excitability, depending on the neuronal cell type.

Complex Subunit Assembly of Neuronal Voltage-gated K+Channels

“…3E). Anti-K v 1.1 specifically labeled a polypeptide of M r 78,000, whereas anti-K v 1.2 yielded very diffuse staining of a polypeptide of about M r 80,000, and anti-K v 1.3 faintly and diffusely stained a polypeptide with an apparent M r of 85,000, all in agreement with previously published data (12,18,27). Anti-K v 1.6 stained a protein of M r 56,000, whereas anti-K v 1.4 failed to react specifically with a polypeptide in cerebellar membranes, although this antibody clearly recognized a polypeptide of M r 95,000 in whole brain membranes (data not shown).…”

“…Moreover, the assembly of distinct K v channel subunits (e.g. K v 1.1/ K v 1.2 (9,11) or K v 1.2/K v 1.4 (10,12)) into functional channel complexes in native brain tissue has been implied.…”

Voltage-Gated K+Channel β Subunits: Expression and Distribution of Kvβ1 and Kvβ2 in Adult Rat Brain

“…In general, the pattern of expression and immunoreactivity for Kv␤2 is best approximated by a composite of that reported for the Kv1.1 and Kv1.2 ␣ subunits (Sheng et al, 1994;Wang et al, 1994;Rhodes et al, 1995). In cerebellar basket-cell terminals, the pattern of Kv␤2 immunoreactivity corresponds precisely to that ob- Figure 8.…”

“…Because the C-terminal epitope contained within the pan-␤ antibody is present in all cloned Kv␤ subunits, it is likely that these ␤-subunit isoforms (designated Kv␤X) also will associate with a subset of the total brain ␤-subunit-containing complexes, i.e., in complexes that also contain Kv␤2. served for Kv1.1 and Kv1.2 (McNamara et al, 1993;Wang et al, 1993Wang et al, , 1994Sheng et al, 1994;Rhodes et al, 1995;Shi et al, 1996), indicating that Kv␤2 is likely to be associated with Kv1.1 and Kv1.2 in these complexes. Similarly, in the juxtaparanodal membrane of myelinated axons, the pattern of Kv␤2 immunoreactivity is identical to that observed for Kv1.1 and Kv1.2 (Wang et al, 1993(Wang et al, , 1994Sheng et al, 1994;Shi et al, 1996).…”

Diverse Expression and Distribution ofShakerPotassium Channels during the Development of theDrosophilaNervous System

“…Abbreviations are as in Figure 2. eration of Kch diversity (Isacoff et al, 1990;Ruppersberg et al, 1990). However, there is compelling evidence in the literature to support both the colocalization and the segregation of different Kch subunits in mammalian brain (Sheng et al, 1992(Sheng et al, , 1994Wang et al, 1993Wang et al, , 1994Scott et al, 1994;Mi et al, 1995;Weiser et al, 1995). PCR , in situ hybridization (TsengCrank et al, 1991), and reporter gene engineering (Mottes and Iverson, 1995) experiments indicate that Sh splice variants can be expressed differentially in some areas of the nervous tissue, retina, and muscle of Drosophila.…”