Splice-variant changes of the Ca(V)3.2 T-type calcium channel mediate voltage-dependent facilitation and associate with cardiac hypertrophy and development.
Low voltage-activated T-type calcium (Ca) channels contribute to the normal development of the heart and are also implicated in pathophysiological states such as cardiac hypertrophy. Functionally distinct T-type Ca channel isoforms can be generated by alternative splicing from each of three different T-type genes (Ca(V)3.1, Ca(V)3.2,Ca(V)3.3), although it remains to be described whether specific splice variants are associated with developmental states and pathological conditions. We aimed to identify and functionally characterize Ca(V)3.2 T-type Ca channel alternatively spliced variants from newborn animals and to compare with adult normotensive and spontaneously hypertensive rats (SHR). DNA sequence analysis of full-length Ca(V)3.2 cDNA generated from newborn heart tissue identified ten major regions of alternative splicing, the more common variants of which were analyzed by quantitative real-time PCR (qRT-PCR) and also subject to functional examination by whole-cell patch clamp. The main findings are that: (1) cardiac Ca(V)3.2 T-type Ca channels are subject to considerable alternative splicing, (2) there is preferential expression of Ca(V)3.2(-25) splice variant channels in newborn rat heart with a developmental shift in adult heart that results in approximately equal levels of expression of both (+25) and (-25) exon variants, (3) in the adult stage of hypertensive rats there is a both an increase in overall Ca(V)3.2 expression and a shift towards expression of Ca(V)3.2(+25) containing channels as the predominant form, and (4) alternative splicing confers a variant-specific voltage-dependent facilitation of Ca(V)3.2 channels. We conclude that Ca(V)3.2 alternative splicing generates significant T-type Ca channel structural and functional diversity with potential implications relevant to cardiac developmental and pathophysiological states.
David
Laurence S
LS
University of British Columbia, Canada.
Garcia
Esperanza
E
Cain
Stuart M
SM
Thau
Elana
E
Tyson
John R
JR
Snutch
Terrance P
TP
D000367:Age Factors; D017398:Alternative Splicing / Q000502:physiology*; D000818:Animals; D000831:Animals, Newborn; D020747:Calcium Channels, T-Type / Q000235:genetics* / Q000502:physiology; D006332:Cardiomegaly / Q000235:genetics*; D022062:Electrophysiologic Techniques, Cardiac / Q000379:methods; D006321:Heart / Q000254:growth & development*; D018408:Patch-Clamp Techniques; D051381:Rats; D011918:Rats, Inbred SHR
C509958:Cacna1h protein, rat; D020747:Calcium Channels, T-Type