Phospholipase C (PLC)-β4 has been considered to be a mammalian homolog of the NorpA PLC, which is responsible for visual signal transduction in Drosophila.We reported previously the cloning of a cDNA encoding rat phospholipase C-β4 (PLC-β4) (Kim, M. J., Bahk, Y. Y., Min, D. S., Lee, S. J., Ryu, S. H., and Suh, P.-G. (1993) Biochem. Biophys. Res. Commun. 194, 706–712). We report now the isolation and characterization of a splice variant (PLC-β4b). PLC-β4b is identical to the 130-kDa PLC-β4 (PLC-β4a) except that the carboxyl-terminal 162 amino acids of PLC-β4a are replaced by 10 distinct amino acids. The existence of PLC-β4b transcripts in the rat brain was demonstrated by reverse transcription-polymerase chain reaction analysis. Immunological analysis using polyclonal antibody specific for PLC-β4b revealed that this splice variant exists in rat brain cytosol. To investigate functional differences between the two forms of PLC-β4, transient expression studies in COS-7 cells were conducted. We found that PLC-β4a was localized mainly in the particulate fraction of the cell, and it could be activated by Gαq, whereas PLC-β4b was localized exclusively in the soluble fraction, and it could not be activated by Gαq. In addition, both PLC-β4a and PLC-β4b were not activated by G-protein βγ-subunits purified from rat brain. These results suggest that PLC-β4b may be regulated by a mechanism different from that of PLC-β4a, and therefore it may play a distinct role in PLC-mediated signal transduction. Phospholipase C (PLC)-β4 has been considered to be a mammalian homolog of the NorpA PLC, which is responsible for visual signal transduction in Drosophila.We reported previously the cloning of a cDNA encoding rat phospholipase C-β4 (PLC-β4) (Kim, M. J., Bahk, Y. Y., Min, D. S., Lee, S. J., Ryu, S. H., and Suh, P.-G. (1993) Biochem. Biophys. Res. Commun. 194, 706–712). We report now the isolation and characterization of a splice variant (PLC-β4b). PLC-β4b is identical to the 130-kDa PLC-β4 (PLC-β4a) except that the carboxyl-terminal 162 amino acids of PLC-β4a are replaced by 10 distinct amino acids. The existence of PLC-β4b transcripts in the rat brain was demonstrated by reverse transcription-polymerase chain reaction analysis. Immunological analysis using polyclonal antibody specific for PLC-β4b revealed that this splice variant exists in rat brain cytosol. To investigate functional differences between the two forms of PLC-β4, transient expression studies in COS-7 cells were conducted. We found that PLC-β4a was localized mainly in the particulate fraction of the cell, and it could be activated by Gαq, whereas PLC-β4b was localized exclusively in the soluble fraction, and it could not be activated by Gαq. In addition, both PLC-β4a and PLC-β4b were not activated by G-protein βγ-subunits purified from rat brain. These results suggest that PLC-β4b may be regulated by a mechanism different from that of PLC-β4a, and therefore it may play a distinct role in PLC-mediated signal transduction. Phosphoinositide-specific phospholipase C (PLC) 1The abbreviations used are: PLC, phospholipase C; IP, inositol phosphate; IP3, inositol 1,4,5-trisphosphate; PI, phosphatidylinositol; PIP2, phosphatidylinositol 4,5-bisphosphate; G-protein, heterotrimeric guanine nucleotide binding protein; PCR, polymerase chain reaction; PBS, phosphate-buffered saline; TBS, Tris-buffered saline; Ins, free inositol fraction; RACE, rapid amplification of cDNA ends; bp, base pair(s). plays a pivotal role in transmembrane signaling. In response to various extracellular stimuli such as numerous hormones, growth factors, and neurotransmitters, this enzyme catalyzes the hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP2) and thereby generates two second messengers, diacylglycerol and inositol 1,4,5-trisphosphate (IP3) (1Berridge M.J. Helslop J.P. Irvine R.F. Brown K.D. Biochem. J. 1984; 222: 195-201Crossref PubMed Scopus (317) Google Scholar, 2Berridge M.J. Irvine R.F. Nature. 1984; 312: 315-321Crossref PubMed Scopus (4254) Google Scholar). Diacylglycerol is a direct activator of protein kinase C, whereas IP3 induces transient release of calcium from the endoplasmic reticulum into the cytoplasm (3Nishizuka Y. Science. 1992; 258: 607-614Crossref PubMed Scopus (4232) Google Scholar). Multiple PLC isozymes have been purified from a variety of mammalian tissues, and several PLC genes have been cloned (4Rhee S.G. Suh P.-G. Ryu S.H. Lee S.Y. Science. 1989; 244: 546-550Crossref PubMed Scopus (699) Google Scholar, 5Rhee S.G. Choi K.D. Adv. Second Messenger Phosphoprotein Res. 1992; 26: 35-61PubMed Google Scholar). As predicted from the cDNAs, the PLC isozymes vary in size, with molecular masses ranging from 85 to 150 kDa. Despite low overall homology among the predicted amino acid sequences, significant sequence similarity exists in two domains that are designated as the X- and the Y-domains. These domains appear to constitute regions important for catalytic activities such as the specific recognition of the substrate and the hydrolysis of its phosphodiester bond. On the basis of the relative locations of the X- and Y-domains in the primary structure, PLC isozymes are classified into three types: β, γ, and δ. All PLC-β types have a carboxyl-terminal 400-amino acid domain that contains an unusually high number of charged residues. On the other hand, the γ type has a long stretch of sequence between the X- and Y-domains, and the δ type contains neither of the two additional sequences (4Rhee S.G. Suh P.-G. Ryu S.H. Lee S.Y. Science. 1989; 244: 546-550Crossref PubMed Scopus (699) Google Scholar, 5Rhee S.G. Choi K.D. Adv. Second Messenger Phosphoprotein Res. 1992; 26: 35-61PubMed Google Scholar, 6Rhee S.G. Bae Y.S. J. Biol. Chem. 1997; 272: 15045-15048Abstract Full Text Full Text PDF PubMed Scopus (817) Google Scholar). As expected from their distinct structural features and their different cellular expression patterns, the PLC isozymes are distinct in their modes of activation in response to extracellular stimuli. The two γ type PLCs, PLC-γ1 and -γ2, but not the β and δ type isozymes, are activated through tyrosyl phosphorylation by growth factor receptor tyrosine kinase or nonreceptor tyrosine kinases (6Rhee S.G. Bae Y.S. J. Biol. Chem. 1997; 272: 15045-15048Abstract Full Text Full Text PDF PubMed Scopus (817) Google Scholar). On the other hand, the PLC-β types (β1, β2, β3) have been shown in cotransfection assays and in in vitro reconstitution experiments to be activated by the αq-subunit of heterotrimeric G-protein (7Smrcka A.V. Hepler J.R. Brown K.O. Sternweis P.C. Science. 1991; 252: 804-807Crossref Scopus (706) Google Scholar, 8Taylor S.J. Chae H.Z. Rhee S.G. Exton J.H. Nature. 1991; 350: 516-518Crossref PubMed Scopus (616) Google Scholar, 9Wu D.Q. Lee C.H. Rhee S.G. Simon M.I. J. Biol. Chem. 1992; 267: 1811-1817Abstract Full Text PDF PubMed Google Scholar, 10Jhon D.-Y. Lee H.-H. Park D. Lee C.-W. Lee K.-H. Yoo O.J. Rhee S.G. J. Biol. Chem. 1993; 268: 6654-6661Abstract Full Text PDF PubMed Google Scholar) and also by the βγ-subunit (11Camps M. Carozzi A. Schnabel P. Scheer A. Parker P.J. Gierschik P. Nature. 1992; 360: 684-686Crossref PubMed Scopus (515) Google Scholar, 12Katz A. Wu D. Simon M.I. Nature. 1992; 360: 686-689Crossref PubMed Scopus (419) Google Scholar, 13Park D. Jhon D.-Y. Lee C.-W. Lee K.-H. Rhee S.G. J. Biol. Chem. 1993; 268: 4573-4576Abstract Full Text PDF PubMed Google Scholar, 14Smrcka A.V. Sternweis P.C. J. Biol. Chem. 1993; 268: 9667-9674Abstract Full Text PDF PubMed Google Scholar, 15Boyer J.L. Graber S.G. Waldo G.L. Harden T.K. Garrison J.C. J. Biol. Chem. 1994; 269: 2814-2819Abstract Full Text PDF PubMed Google Scholar, 16Ueda N. Iniguez-Lluhi J.A. Lee E. Smrcka A.V. Robishaw J.D. Gilman A.G. J. Biol. Chem. 1994; 269: 4388-4395Abstract Full Text PDF PubMed Google Scholar, 39Wu D. Katz A. Simon M.I. Proc. Natl. Acad. Sci. U. S. A. 1993; 90: 5297-5301Crossref PubMed Scopus (174) Google Scholar). Additionally, it is known that the carboxyl-terminal tail that follows the Y-domain is involved in the activation of PLC-β type by Gαq (17Wu D. Jiang H. Katz A. Simon M.I. J. Biol. Chem. 1993; 268: 3704-3709Abstract Full Text PDF PubMed Google Scholar,42Park D. Jhon D.Y. Lee C.W. Ryu S.H. Rhee S.G. J. Biol. Chem. 1993; 268: 3710-3714Abstract Full Text PDF PubMed Google Scholar, 43Lee S.B. Shin S.H. Hepler J.R. Gilman A.G. Rhee S.G. J. Biol. Chem. 1993; 268: 25952-25957Abstract Full Text PDF PubMed Google Scholar, 44Kim C.G. Park D. Rhee S.G. J. Biol. Chem. 1996; 271: 21187-21192Abstract Full Text Full Text PDF PubMed Scopus (193) Google Scholar). Previously, Min et al. (18Min D.S. Kim D.M. Lee Y.H. Seo J. Suh P.G. Ryu S.H. J. Biol. Chem. 1993; 268: 12207-12212Abstract Full Text PDF PubMed Google Scholar, 19Min D.S. Kim Y. Lee Y.H. Suh P.G. Ryu S.H. FEBS Lett. 1993; 331: 38-42Crossref PubMed Scopus (13) Google Scholar) purified the 97-kDa and the 130-kDa PLC-β4 enzymes from bovine cerebellum. cDNA encoding a 130-kDa PLC-β4 has been isolated (20Kim M.J. Bahk Y.Y. Min D.S. Lee S.J. Ryu S.H. Suh P.G. Biochem. Biophys. Res. Commun. 1993; 194: 706-712Crossref PubMed Scopus (24) Google Scholar, 33Ferreira P.A. Shortridge R.D. Pak W.L. Proc. Natl. Acad. Sci. U. S. A. 1993; 90: 6042-6046Crossref PubMed Scopus (51) Google Scholar, 38Lee C.W. Park D.J. Lee K.H. Kim C.G. Rhee S.G. J. Biol. Chem. 1993; 268: 21318-21327Abstract Full Text PDF PubMed Google Scholar). Based on these studies, it has been suggested that PLC-β4 might be a mammalian homolog of the Drosophila NorpA PLC, which is responsible for photosignal transduction. Furthermore, recent results obtained from cotransfection assays and in vitro reconstitution experiments showed that PLC-β4 could be activated by Gαq but not by βγ-subunits of G-proteins (21Jiang H. Wu D. Simon M.I. J. Biol. Chem. 1994; 269: 7593-7596Abstract Full Text PDF PubMed Google Scholar,22Lee C.-W. Lee K.-H. Lee S.B. Rhee S.G. J. Biol. Chem. 1994; 269: 25335-25338Abstract Full Text PDF PubMed Google Scholar). Here we report the identification of a rat PLC-β4 variant with a different carboxyl-terminal region. We show by reverse transcription-PCR and immunoblot analysis that this new splice variant of PLC-β4 exists in vivo. Furthermore, we further demonstrate that this splice variant is neither associated with the particulate fraction of the cell, nor is it activated by Gαq. In the course of isolating PLC-β4 cDNA from a rat brain λZapII cDNA library (20Kim M.J. Bahk Y.Y. Min D.S. Lee S.J. Ryu S.H. Suh P.G. Biochem. Biophys. Res. Commun. 1993; 194: 706-712Crossref PubMed Scopus (24) Google Scholar), we identified cDNA clones and which of enzyme from the previously 130-kDa PLC-β4 cDNA sequence analysis of these revealed that were splice of the PLC-β4 and were purified and into by in with The sequences were from clones by the and chain S. Proc. Natl. Acad. Sci. U. S. A. PubMed Scopus Google Scholar). was from rat brain using the P. N. Biochem. PubMed Scopus Google Scholar). cDNA was in a reaction 10 of 10 of and of reverse a the reaction was by for of the reaction was used for was in a reaction 10 of of and of polymerase The reaction for of for for and for The two used amino acids of the PLC-β4b and which is the specific for the PLC-β4b The were in a with rat brain from was reverse with The cDNA was used as for amplification using the the of PLC-β4a and which is also specific for PLC-β4b The was into and by the the of PLC-β4a was by an of and a of used was from of The cDNA was into of and The of a the cDNA for PLC-β4b was by the of with the of which been by in of of between of The mammalian expression for PLC-β4a and PLC-β4b were by the of and into the of The were and mammalian expression for Gαq was the with the from using Gαq cDNA as with the and the are were to to the of Gαq regions of and The was with and into the of and the was All sequences were by COS-7 cells were in with of the COS-7 cells was by the Nature. 1984; PubMed Scopus Google Scholar). were and by with of of and of in for of was the was and the cells were with in for with PBS, and in a The cells were to of PLC-β4a or and to of were by to with and into as Y.Y. Lee Y.H. Lee Seo J. Ryu S.H. Suh P.-G. J. Biol. Chem. 1994; 269: Full Text PDF PubMed Google Scholar). were purified on protein The polyclonal antibody used in was a from Y. S. Kim rat were in a with of and The was for The was to with and to a 10 with A. The were with a from to in A. All were by with the antibody the sequence that protein by the antibody were with The fraction the with and was used for analysis. COS-7 with expression the cDNA of PLC-β4a or were in and by The was for in a The fraction was from the particulate were by and The were with antibody the amino acids of PLC-β4, and the was with a of antibody and using the The expression of PLC-β4b protein in by using expression was as previously M. G.L. J. 1984; PubMed Google Scholar). were with and with that in The brain was in the and on a into of the were for with in to the binding of The were with and PLC-β4a and in and for the were three for 10 with TBS, for with or in and three for 10 with TBS, and for with in three with the were with in TBS, COS-7 cells were with and or the cells were with in The cells were with and in free for the 10 of the was The cells were with and for The reaction was by of the and the with inositol was as previously A. Exton J.H. J. Biol. Chem. 1994; 269: Full Text PDF PubMed Google Scholar). were with of acid for on The cells were the and was by of was with of and a inositol was three with of inositol fraction, and the was three with of and the inositol was with of and acid inositol fraction, of of the and was with 10 of and A. Exton J.H. J. Biol. Chem. 1994; 269: Full Text PDF PubMed Google Scholar). The are as the of by In addition, by activities of with the of in the was expression for PLC-β4a, or were into COS-7 COS-7 cells were with and with 10 and for the were in the in vitro PLC of COS-7 cells were with 10 and were as and 4,5-bisphosphate were in a of The were to a of and in a type for 10 in and The of 4,5-bisphosphate in the was with The PLC was in a of of the COS-7 cells of the βγ-subunits by Park of and and of the of free to The reaction was with the of the and by of by were with of in an for the of in the was for by We isolated two clones and that enzyme from the 130-kDa PLC-β4 reported sequence analysis revealed that these clones could be a splice variant of the 130-kDa PLC-β4 was for further analysis it the cDNA The overall cDNA of was identical to the 130-kDa PLC-β4 except that this a from the encoding the carboxyl-terminal of the 130-kDa PLC-β4 a with the of the 130-kDa PLC-β4 As a the carboxyl-terminal 162 amino acids are replaced with 10 distinct amino acids in As in the variant of its sequence with the 130-kDa PLC-β4 but it also has its that are not in the 130-kDa PLC-β4 and are from the the between the two is to the or of two specific it is that the variant from an it be that is the of a different The encoding the splice variant of PLC-β4 the of the In an to a encoding the of this splice we two other rat brain cDNA but we to that was on the results obtained from studies using we could that the protein by the variant the with the 130-kDa PLC-β4 we used the long cloning to PLC-β4b an identical primary with rat brain was reverse with The cDNA was used as for long amplification using the sequence the of PLC-β4a as and an to the of amplification a and The of this was the as the with as a and this we that PLC-β4b has an identical to the PLC-β4a The predicted by the sequences of the clones and the long for a of amino acids with a molecular of number The protein predicted by this sequence was designated whereas the previously reported PLC-β4 was now To a of the variant of PLC-β4 exists in we reverse We used from rat brain for reverse with The used in the were to the to the of the PLC-β4b As shown in the obtained from rat brain and was the expected that a PLC-β4b in and that was not an by we isolated a cDNA encoding PLC-β4b by long PCR, we were not in isolating a the of the splice and we could not the that the PLC-β4b was or a we a different to the that PLC-β4b exists in and the with we could the PLC in rat brain and this protein with an antibody the and an antibody the sequence of PLC-β4a, this that PLC-β4b is an vivo. we two to the carboxyl-terminal of PLC-β4b and the other to the of PLC-β4a we used these in an we PLC-β4b in cells with the cDNA to the molecular of PLC-β4b be the expected in a As shown in the molecular of the PLC-β4b in cells was the predicted and it was by both the antibody and the antibody in to PLC-β4b in we rat brain on a All were and with The protein by the antibody with The fraction the with not and was used for the immunoblot analysis. fraction was also by the antibody in both with from of we that PLC-β4b a with To functional differences of the two forms of PLC-β4, we their studies suggested that the carboxyl-terminal of the PLC-β type is for their with the particulate fraction of the (17Wu D. Jiang H. Katz A. Simon M.I. J. Biol. Chem. 1993; 268: 3704-3709Abstract Full Text PDF PubMed Google Scholar, mammalian expression PLC-β4a or PLC-β4b was into COS-7 The cells were into a soluble fraction and a particulate fraction, of which was with As in the of PLC-β4a is localized in the particulate fraction, whereas PLC-β4b is found exclusively in the soluble In addition, the of PLC-β4b in the of rat was with PLC-β4b was in the cytoplasm of not we have immunoblot analysis of the particulate fraction of the rat brain by using PLC-β4b was not in the particulate fraction of the rat brain not These results are with that PLC-β4b is found in the fraction of the rat brain PLC-β4b is localized exclusively in the fraction and the carboxyl-terminal of is for both its with the particulate fraction and its activation by Gαq (17Wu D. Jiang H. Katz A. Simon M.I. J. Biol. Chem. 1993; 268: 3704-3709Abstract Full Text PDF PubMed Google Scholar), we PLC-β4a and PLC-β4b for their to be activated by Gαq. COS-7 cells were with the mammalian expression for Gαq and a cDNA PLC-β4a or was to the G-protein J. P. M. J. PubMed Scopus Google Scholar). As in with or with PLC-β4a or PLC-β4b to a low of inositol was in with the cells were with the mammalian expression for PLC-β4a and Gαq, was a significant in inositol cells with the expression for PLC-β4b and Gαq showed in inositol with that of cells with the Gαq expression To the that the in the of Gαq on PLC-β4b was the of a expression of PLC-β4 or Gαq in COS-7 we an immunoblot analysis using antibody and was that the of PLC-β4a was to that of PLC-β4b and that the expression of Gαq and in the COS-7 cells were not by the cotransfection Furthermore, in a the of PLC-β4b purified from of cells with the cDNA was of specific was to that of the 130-kDa PLC-β4a purified from bovine that the PLC-β4b variant was as as the 130-kDa PLC-β4a not that the carboxyl-terminal of PLC-β4a is important for activation by Gαq, but it is not important for the PLC of the PLC-β4 Previously, al. Y. S. Y. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, Y. Y. FEBS Lett. 1994; PubMed Scopus Google Scholar) reported that the activation of a carboxyl-terminal of by be by brain G-protein βγ-subunits that of the We a carboxyl-terminal be activated by G-protein this mammalian expression for PLC-β4a, or PLC-β4b were into COS-7 The were with G-protein βγ-subunits purified from rat and in vitro PLC was that in with of activated by G-protein βγ-subunits (21Jiang H. Wu D. Simon M.I. J. Biol. Chem. 1994; 269: 7593-7596Abstract Full Text PDF PubMed Google Scholar, C.-W. Lee K.-H. Lee S.B. Rhee S.G. J. Biol. Chem. 1994; 269: 25335-25338Abstract Full Text PDF PubMed Google Scholar), the of is by the G-protein whereas PLC-β4a and PLC-β4b are not activated by the G-protein These suggest that PLC-β4a and PLC-β4b are not for by G-protein PLC-β4 has been considered to be a mammalian homolog of PLC, which is responsible for visual signal transduction in Drosophila W.L. Sci. Google Scholar, Kim S. Shortridge R.D. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, P. M. M. N. J. PubMed Scopus Google Scholar). results obtained from in of rat brain and from a that PLC-β4 suggest that PLC-β4 may play a significant role in mammalian visual P.A. Pak W.L. J. Biol. Chem. 1994; 269: Full Text PDF PubMed Google Scholar, H. A. N. E. D. Simon M.I. Wu D. Proc. Natl. Acad. Sci. U. S. A. 1996; PubMed Scopus Google Scholar). In we isolated a splice variant of rat PLC-β4 and it splice variant has a carboxyl-terminal tail with the previously reported 130-kDa PLC-β4 (20Kim M.J. Bahk Y.Y. Min D.S. Lee S.J. Ryu S.H. Suh P.G. Biochem. Biophys. Res. Commun. 1993; 194: 706-712Crossref PubMed Scopus (24) Google Scholar, 33Ferreira P.A. Shortridge R.D. Pak W.L. Proc. Natl. Acad. Sci. U. S. A. 1993; 90: 6042-6046Crossref PubMed Scopus (51) Google Scholar, 38Lee C.W. Park D.J. Lee K.H. Kim C.G. Rhee S.G. J. Biol. Chem. 1993; 268: 21318-21327Abstract Full Text PDF PubMed Google Scholar). Based on the of the cDNA sequences of the two forms of PLC-β4, we that the mechanism by which PLC-β4b is might be of the To identified splice of the PLC-β type rat Y.Y. Lee Y.H. Lee Seo J. Ryu S.H. Suh P.-G. J. Biol. Chem. 1994; 269: Full Text PDF PubMed Google Scholar), bovine PLC-β4 P.A. Shortridge R.D. Pak W.L. Proc. Natl. Acad. Sci. U. S. A. 1993; 90: 6042-6046Crossref PubMed Scopus (51) Google Scholar), Drosophila R.D. J. Pak W.L. J. Biol. Chem. 1991; Full Text PDF PubMed Google Scholar), and Drosophila NorpA PLC S. Shortridge R.D. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). The in of these PLC isozymes the X- and Y-domains. in the carboxyl-terminal regions of the rat and the Drosophila has been reported Y.Y. Lee Y.H. Lee Seo J. Ryu S.H. Suh P.-G. J. Biol. Chem. 1994; 269: Full Text PDF PubMed Google R.D. J. Pak W.L. J. Biol. Chem. 1991; Full Text PDF PubMed Google Scholar), the that splice may be regulated on differences in the primary is Previously, Wu et al. (17Wu D. Jiang H. Katz A. Simon M.I. J. Biol. Chem. 1993; 268: 3704-3709Abstract Full Text PDF PubMed Google Scholar) have identified regions in which are involved in the activation by Gαq. a of found that the between and is for both of with the particulate fraction and activation by Gαq. also found that the between and is for with the G-protein αq-subunit but is not for of the with the particulate The in is the in the In their the suggested that with the particulate fraction might through or charged In addition, the of the of and for particulate has been reported D. Jhon D.Y. Lee C.W. Ryu S.H. Rhee S.G. J. Biol. Chem. 1993; 268: 3710-3714Abstract Full Text PDF PubMed Google Scholar, 43Lee S.B. Shin S.H. Hepler J.R. Gilman A.G. Rhee S.G. J. Biol. Chem. 1993; 268: 25952-25957Abstract Full Text PDF PubMed Google Scholar, 44Kim C.G. Park D. Rhee S.G. J. Biol. Chem. 1996; 271: 21187-21192Abstract Full Text Full Text PDF PubMed Scopus (193) Google Scholar). We found that the in PLC-β4, the is of the in PLC-β4b PLC-β4a, an additional 162 amino acids in the carboxyl-terminal was localized in the particulate fraction, and it could be activated by Gαq. it that the in PLC-β4 is for the of the protein with the particulate fraction, and the carboxyl-terminal 162 amino acids in PLC-β4a are for the with the particulate fraction and activation by Gαq. the carboxyl-terminal 162 amino acids of PLC-β4a also a number of charged and amino a for the may be the of the charged the of et al. Y. S. Y. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, Y. Y. FEBS Lett. 1994; PubMed Scopus Google Scholar) reported that a carboxyl-terminal of by be activated to a by brain G-protein βγ-subunits the The suggested that the carboxyl-terminal of may its activation by G-protein et al. Y. Wu Y. Smrcka A. Jiang H. Wu D. Proc. Natl. Acad. Sci. U. S. A. 1996; PubMed Scopus Google Scholar) suggested that the to of the is involved in the with the G-protein In their further the to amino acids to in vitro binding assays using and G-protein These to of are the of the regions among PLC it has been known that PLC-β4a be activated by G-protein βγ-subunits in and in previously the of G-protein of the PLC-β4b might by we found that a carboxyl-terminal is to by G-protein results suggest that PLC-β4 and not have the sequence to be activated by G-protein In we have isolated a splice variant of the previously reported rat brain PLC-β4 The two of PLC-β4 and are by of in their and their to activation by the αq-subunit of We therefore that the two forms of PLC-β4 may have distinct in PLC-mediated signal transduction.
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