Expression of T-type calcium channel splice variants in human glioma.
In humans, three isoforms of the T-type (Ca(v)3.1) calcium-channel alpha(1) subunit have been reported as a result of alternate splicing of exons 25 and 26 in the III-IV linker region (Ca(v)3.1a, Ca(v)3.1b or Ca(v)3.1bc). In the present study, we report that human glioma express Ca(v)3.1 channels in situ, that splicing of these exons is uniquely regulated and that there is expression of a glioma-specific novel T-type variant (Ca(v)3.1ac). Seven human glioma samples were collected at surgery, RNA was extracted, and cDNA was produced for RT-PCR analysis. In addition, three glioma cell lines (U87, U563, and U251N), primary cultures of human fetal astrocytes, as well as adult and fetal human brain cDNA were used. Previously described Ca(v)3.1 splice variants were present in glioma samples, cultured cells and whole brain. Consistent with the literature, our results reveal that in the normal adult brain, Ca(v)3.1a transcripts predominate, while Ca(v)3.1b is mostly fetal-specific. RT-PCR results on glioma and glioma cell lines showed that Ca(v)3.1 expression in tumor cells resemble fetal brain expression pattern as Ca(v)3.1bc is predominantly expressed. In addition, we identified a novel splice variant, Ca(v)3.1ac, expressed in three glioma biopsies and one glioma cell line, but not in normal brain or fetal astrocytes. Transient expression of this variant demonstrates that Ca(v)3.1ac displays similar current-voltage and steady-state inactivation properties compared with Ca(v)3.1b, but a slower recovery from inactivation. Taken together, our data suggest glioma-specific Ca(v)3.1 gene regulation, which could possibly contribute to tumor pathogenesis.
Latour
Isabelle
I
Department of Physiology and Biophysics, Faculty of Medicine, University of Calgary, Calgary, Alberta T2N 4N1, Canada.
Louw
Deon F
DF
Beedle
Aaron M
AM
Hamid
Jawed
J
Sutherland
Garnette R
GR
Zamponi
Gerald W
GW
D017398:Alternative Splicing / Q000235:genetics*; D000595:Amino Acid Sequence / Q000235:genetics; D001483:Base Sequence / Q000235:genetics; D001932:Brain Neoplasms / Q000235:genetics* / Q000378:metabolism; D020747:Calcium Channels, T-Type / Q000235:genetics* / Q000378:metabolism; D002460:Cell Line; D018076:DNA, Complementary / Q000032:analysis / Q000235:genetics; D005091:Exons / Q000235:genetics; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics; D005910:Glioma / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D008297:Male; D008564:Membrane Potentials / Q000235:genetics; D008969:Molecular Sequence Data; D018408:Patch-Clamp Techniques; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012016:Reference Values
C121855:CACNA1G protein, human; D020747:Calcium Channels, T-Type; D018076:DNA, Complementary; D020033:Protein Isoforms; D012333:RNA, Messenger