Differential expression of BK channel isoforms and β-subunits in rat neuro-vascular tissues

We investigated the expression of splice variants and beta-subunits of the BK channel (big conductance Ca2+- activated K+ channel, Slo1, MaxiK, K(ca)1.1) in rat cerebral blood vessels, meninges, trigeminal ganglion among other tissues. An alpha-subunit splice variant X1(+24) was found expressed (RT-PCR) in nervous tissue only where also the SS4(+81) variant was dominating with little expression of the short form SS4(0). SS4(+81) was present in some cerebral vessels too. The SS2(+174) variant (STREX) was found in both blood vessels and in nervous tissue. In situ hybridization data supported the finding of SS4(+81) and SS2(+174) in vascular smooth muscle and trigeminal ganglion. beta-subunits beta 2 and beta 4 showed high expression in brain and trigeminal ganglion and some in cerebral vessels while beta 1 showed highest expression in blood vessels. beta 3 was found only in testis and possibly brain. A novel splice variant X2(+92) was found, which generates a stop codon in the intracellular C-terminal part of the protein. This variant appears non-functional as a homomer but may modulate the function of other splice-variants when expressed in Xenopus oocytes. In conclusion a great number of splice variant and beta-subunit combinations likely exist, being differentially expressed among nervous and vascular tissues. (c) 2008 Elsevier B.V. All rights reserved.