The extreme C-terminal region of phospholipase Cbeta1 determines subcellular localization and function; the "b" splice variant mediates alpha1-adrenergic receptor responses in cardiomyocytes.
Phospholipase Cbeta1 (PLCbeta1) exists as two splice variants, PLCbeta1a (150 kDa) and PLCbeta1b (140 kDa), which differ only in their C-terminal sequences of 64 and 31 amino acids, respectively. The 3 C-terminal amino acid residues of PLCbeta1a comprise a PDZ-interacting domain, whereas the PLCbeta1b sequence has no PDZ-interacting domain but contains unique proline-rich domain 5 residues from the C terminus. PLCbeta1a is localized in the cytoplasm, whereas PLCbeta1b targets to the sarcolemma and is enriched in caveolae. Deletion of 3 amino acids from the C terminus of PLCbeta1b did not alter its sarcolemmal localization, but deletion of the entire unique 31 amino acid sequence caused cytosolic localization. A myristoylated 10 amino acid peptide from the C terminus of PLCbeta1b selectively dissociated N-terminally GFP-tagged PLCbeta1b from the sarcolemma and inhibited PLC responses to alpha(1)-adrenergic agonists, with a half maximal effective concentration of 12 +/- 1.6 microM (mean+/-SE, n=3). A similar peptide from PLCbeta1a was without effect at concentrations below 100 microM. Thus, the extreme C-terminal sequences of the PLCbeta1 splice variants determine localization and, thus, function. In cardiomyocytes, responses initiated by alpha(1)-adrenergic receptor activation involve only PLCbeta1b, and the selective targeting of this splice variant to the sarcolemma provides a potential therapeutic target to reduce hypertrophy, apoptosis, and arrhythmias.
Grubb
David R
DR
Cellular Biochemistry Laboratory, Baker Heart Research Institute, Melbourne, Victoria, Australia.
Vasilevski
Oliver
O
Huynh
Huy
H
Woodcock
Elizabeth A
EA
D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D043802:GTP-Binding Protein alpha Subunits, Gq-G11 / Q000378:metabolism; D066298:In Vitro Techniques; D032383:Myocytes, Cardiac / Q000201:enzymology / Q000378:metabolism* / Q000648:ultrastructure; D054799:Phospholipase C beta / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D051381:Rats; D017207:Rats, Sprague-Dawley; D018340:Receptors, Adrenergic, alpha-1 / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012508:Sarcolemma / Q000201:enzymology; D017384:Sequence Deletion; D013347:Subcellular Fractions / Q000201:enzymology
D018340:Receptors, Adrenergic, alpha-1; D011994:Recombinant Proteins; D054799:Phospholipase C beta; C518035:Plcb1 protein, rat; D043802:GTP-Binding Protein alpha Subunits, Gq-G11