Splice Isoforms of Phosducin-like Protein Control the Expression of Heterotrimeric G Proteins

Abstract

Background: Heterotrimeric G proteins are essential for biological signaling; however, the mechanism of their biosynthesis remains poorly understood. Results: Long and short splice isoforms of phosducin-like protein stimulate and inhibit production of G proteins in the cell. Conclusion: Both G protein ␣ and ␤␥ functional units are subject to the regulation. Significance: We describe a potential mechanism for regulating the cellular levels of G proteins.

Essential Role of the Chaperonin CCT in Rod Outer Segment Biogenesis

“…All of these proteins were also found to be significantly reduced in the photoreceptors of the PhLPs-expressing transgenic mice used in the present study. 28,31 However, due to the broader nature of the CCT suppression by the dominant-negative PhLPs, additional proteins become affected in this animal model, including those essential for outer segment biogenesis. It should be mentioned that in this, as well as our previous studies, 28,31 the suppression CCT by PhLPs didn't seem to have a significant impact on cytoskeletal proteins, actin and tubulin, known to be processed by CCT.…”

“…It is also consistent with the notion that CCT particles engaged in the folding of actin and tubulin are not available to interact with PhLPs, which predominantly targets CCT preloaded with nascent G protein b subunits. 31 Therefore, the high levels of actin and tubulin expression in the cell may keep this biosynthetic pathway protected from suppression by PhLPs.…”

“…The CCT complex in human cell lines could be efficiently sequestered by overexpressing mouse D1-83 PhLP-FLAG. 31 Phosducin, a close homolog of phosducin-like protein that doesn't interact with CCT, was used as a negative control, and tdTomato was used as a red fluorescent marker to identify the transfected cells (Figs. 7A, 7B).…”

“…34 Alternative splicing of the phosducin-like protein gene (PDCL) gives rise to an isoform designated PhLPs (for ''short''), which forms a high-affinity complex with CCT, leading to its inactivation. 31 We used PhLPs as a tool to inhibit the CCT activity in mice, which normally do not express this splice isoform. 31 Phosducin-like proteins were expressed in retinal photoreceptors under the control of a rhodopsin promoter from a transgene designated as D1-83 PhLP-FLAG, containing the same N-terminal deletion as PhLPs as well as a C-terminal epitope tag.…”

“…31 We used PhLPs as a tool to inhibit the CCT activity in mice, which normally do not express this splice isoform. 31 Phosducin-like proteins were expressed in retinal photoreceptors under the control of a rhodopsin promoter from a transgene designated as D1-83 PhLP-FLAG, containing the same N-terminal deletion as PhLPs as well as a C-terminal epitope tag. Three transgenic lines (1-3) expressed different levels of D1-83 PhLP-FLAG, detectable already at P08 .…”