Lipid storage provides energy stores for the body in times of increased oxidative requirements, such as fasting or exercise, but when the balance of lipid storage and mobilization is disrupted human ...health suffers. Implications for increased lipid storage include risk factors for developing type II diabetes mellitus and non‐alcoholic fatty liver disease. The perilipin family of proteins associate with the surface of lipid droplets and are essential to regulation of stored triacylglycerols. Perilipin 5 functions to maintain a balance between the storage of triacylglycerols in lipid droplets or their mobilization when energetically required. Several members of the perilipin gene family exhibit differential splicing, most notably perilipin 1 but reports exist of alternative messages for shortened forms of perilipins 2 and 3. We have identified a shortened form of perilipin 5 we have termed perilipin 5b. Western blots indicate that the protein, of approximately 35 kDa, is present in C2C12 cultured myoblasts and in heart and liver tissue from fed and fasted mice. Analysis of murine genomic DNA sequences reveals stop codons found in the introns between exons 6 and 7 and 7 and 8, either of which could give rise to a protein of approximately 35 kDa, indicating the likelihood of the observed protein being a splice variant, rather than a post‐translationally modified protein. Using RT‐PCR we have identified multiple amplicons suggesting that perilipin‐5b contains a read through of intron 6 of the murine perilipin 5 gene. Mining transcriptome databases reveals several transcripts with retained introns. Analysis of the amino acid sequence of perilipin 5b indicates that this truncation would lack the reported C‐terminal domain essential for interactions with ATGL and CGI‐58 but would retain the PKA site found at Ser155. The function of perilipin 5b is yet unknown, but the fact that it is found primarily in heart tissue seems to suggest that it plays a role in the oxidation of the lipid droplet. These data are consistent with what is currently known about Perilipin‐5 and the other PAT family proteins. Determination of perilipin 5b function will give a more accurate picture of the overall mechanism of lipid storage and metabolism.
The PAT family of lipid droplet proteins includes 5 members in mammals: perilipin, adipose differentiation-related protein (ADRP), tail-interacting protein of 47 kDa (TIP47), S3–12, and OXPAT. ...Members of this family are also present in evolutionarily distant organisms, including insects, slime molds and fungi. All PAT proteins share sequence similarity and the ability to bind intracellular lipid droplets, either constitutively or in response to metabolic stimuli, such as increased lipid flux into or out of lipid droplets. Positioned at the lipid droplet surface, PAT proteins manage access of other proteins (lipases) to the lipid esters within the lipid droplet core and can interact with cellular machinery important for lipid droplet biogenesis. Genetic variations in the gene for the best-characterized of the mammalian PAT proteins, perilipin, have been associated with metabolic phenotypes, including type 2 diabetes mellitus and obesity. In this review, we discuss how the PAT proteins regulate cellular lipid metabolism both in mammals and in model organisms.
Obesity, type II diabetes mellitus, and non‐alcoholic fatty liver disease are all diseases associated with dysfunction of lipid metabolism or lipid mobilization – the breakdown of lipids into free ...fatty acids and glycerol. Because of this, research done on topics related to lipid metabolism provides potentially valuable insight into disease pathogenesis. Neutral lipids in the cell are stored in lipid storage droplets coated with at least one of the perilipin family of proteins, essential regulators of lipase function. Previous work by other laboratories has indicated that the carboxy terminus of perilipin 3 folds into a boot‐like structure consisting of a four‐helix bundle capped by a mixed α‐β domain. At the interface of the four‐helix bundle and the mixed α‐β domain is a hydrophobic cleft of unknown function. The genomic organization, nucleotide sequence, and amino acid sequence of perilipins 3 and 5 are highly conserved, particularly in the region that contains this hydrophobic cleft. Threading the sequence of perilipin 5 onto perilipin 3 using both RAPTOR X and PHYRE 2 produces a similar structure that also includes conservation of the pocket of interest. To study interactions of the hydrophobic pocket, models of the proteins were docked in silico to a series of small organic biological molecules using the GOLD software package from Cambridge Crystallographic Database. Mono and bicyclic systems were docked and yielded CHEMPLP scores ranging from approximately 25 to 45. Docking results were visualized and verified and fits compared using the molecular visualization software HERMES. Examination of current results informed future decisions of which candidate molecules to attempt to dock. The increasing CHEMPLP scores for the molecules examined, and their fits into the pocket seen in Hermes, indicate that a small molecule may bind to this pocket, potentially impacting the biological function of this class of proteins. Additionally, this work may provide a means for development of small molecules which could be used as possible pharmacological interventions for the treatment of lipid storage disorders.
Obesity, type II diabetes mellitus, and non‐alcoholic fatty liver disease are all conditions related to aberrant lipid storage in the organism. Nearly all cells have the capacity to store neutral ...lipids in lipid storage droplets, organelles that regulate the storage of their hydrophobic contents. All lipid storage droplets are coated with at least one member of the perilipin family of proteins. These proteins serve as a substrate of protein kinase A, act as cofactors for lipases, are implicated in lipid trafficking, and have been shown to act as transcriptional coactivators. Perilipin 5 is expressed in tissues including oxidative muscle and fasted liver and has been shown to play important roles in neutral lipid metabolism in these tissues and metabolic states. The mechanism through which perilipin 5 enters the nucleus is not known. Using a cultured cell model expressing either perilipin 5 or a perilipin 5 3X‐FLAG fusion protein, assayed with immunoblotting and immunofluorescence microscopy we have observed protein kinase A dependent phosphorylation of perilipin 5 and translocation of perilipin 5 to the cytosol and nucleus. There are five known mechanisms for large molecules to gain entry to the nucleus through the nuclear pore. We have used multiple compounds to attempt to block entry of perilipin 5. Preliminary results indicate that the synthetic steroid mifepristone, but not other inhibitors, block entry, implicating the importin α/β1 nuclear transport pathway in this process. These data indicate that the biological function of perilipin 5 can be at least partially blocked pharmacologically using commercially available drugs. This presents an interesting potential for further examination and treatment of metabolic diseases.
A key step in lipolytic activation of adipocytes is the translocation of hormone-sensitive lipase (HSL) from the cytosol to the surface of the lipid storage droplet. Adipocytes from perilipin-null ...animals have an elevated basal rate of lipolysis compared with adipocytes from wild-type mice, but fail to respond maximally to lipolytic stimuli. This defect is downstream of the β-adrenergic receptor-adenylyl cyclase complex. Now, we show that HSL is basally associated with lipid droplet surfaces at a low level in perilipin nulls, but that stimulated translocation from the cytosol to lipid droplets is absent in adipocytes derived from embryonic fibroblasts of perilipin-null mice. We have also reconstructed the HSL translocation reaction in the nonadipocyte Chinese hamster ovary cell line by introduction of GFP-tagged HSL with and without perilipin A. On activation of protein kinase A, HSL-GFP translocates to lipid droplets only in cells that express fully phosphorylatable perilipin A, confirming that perilipin is required to elicit the HSL translocation reaction. Moreover, in Chinese hamster ovary cells that express both HSL and perilipin A, these two proteins cooperate to produce a more rapidly accelerated lipolysis than do cells that express either of these proteins alone, indicating that lipolysis is a concerted reaction mediated by both protein kinase A-phosphorylated HSL and perilipin A.
Adipose differentiation-related protein (ADRP) is localized to lipid droplets in most mammalian cells. ADRP, proposed to regulate fatty acid mobilization and lipid droplet formation, is linked to ...lipid accumulation in foam cells of human atherosclerotic lesions. In this report, we show that ADRP protein accumulates in Chinese hamster ovary fibroblastic cells cultured in the presence of oleic acid but is destabilized when fatty acid sources are removed from culture serum. The latter effect was blocked by the proteasome inhibitor MG132, whereas inhibitors of other proteolytic processes were ineffective. Pulse-chase experiments confirmed that ADRP degradation is inhibited by MG132. Conditions that stimulate ADRP degradation also promoted the covalent modification of ADRP by ubiquitin, whereas the addition of oleic acid to culture media, which promotes triacylglycerol deposition, blunted the appearance of ubiquitinated-ADRP. Treatment with MG132 increased the levels of ADRP associated with lipid droplets, as well as throughout the cytosol. Finally, we demonstrate that the disappearance of ADRP protein after the onset of perilipin expression during adipocyte differentiation is due to degradation by proteasomes Thus, proteolytic degradation of ADRP mediated through the ubiquitin/proteasome pathway appears to be a major mode for the post-translational regulation of ADRP.
The related disorders of obesity and diabetes are increasing to epidemic proportions. The role of neutral lipid storage and hydrolysis, and hence the adipocyte, is central to understanding this ...phenomenon. The adipocyte holds the major source of stored energy in the body in the form of triacylglycerols (TAG). It has been known for over 35 years that the breakdown of TAG and release of free (unesterified) fatty acids and glycerol from fat tissue can be regulated by a cAMP‐mediated process. However, beyond the initial signaling cascade, the mechanistic details of this lipolytic reaction have remained unclear. Work in recent years has revealed that both hormone‐sensitive lipase (HSL), generally thought to be the rate‐limiting enzyme, and perilipin, a lipid droplet surface protein, are required for optimal lipid storage and fatty acid release. There are multiple perilipin proteins encoded by mRNA splice variants of a single perilipin gene. The perilipin proteins are polyphosphorylated by protein kinase A and phosphorylation is necessary for translocation of HSL to the lipid droplet and enhanced lipolysis. Hence, the surface of the lipid storage droplet has emerged as a central site of regulation of lipolysis. This review will focus on adipocyte lipolysis with emphasis on hormone signal transduction, lipolytic enzymes, the lipid storage droplet, and fatty acid release from the adipocyte. IUBMB Life, 56: 379‐385, 2004
Modern students have grown up surrounded by stunning graphics and visual imagery. At the same time, advances in technology and how data are visualized has changed the practice of science. How do ...these two observations work for and against educators? A generation ago simple line drawings would have sufficed in a printed biochemistry text, but this is no longer the case. As digital media has progressed and ways that scientists represent data has changed, we as educators should ask if the two complement one another. In other words, can the images found in biochemistry help educators tell the story and enable student to better learn biochemistry? Are images a distraction, or, at worst, do figures in biochemistry teach misconceptions about biochemical principles? This talk will use examples of figures from a new work to show how art can help drive student understanding in biochemistry and help overall comprehension and higher‐order thinking.
This is from the Experimental Biology 2019 Meeting. There is no full text article associated with this published in The FASEB Journal.
The impacts of science are felt across all socio-ecological levels, ranging from the individual to societal. In order to adapt or respond to scientific discoveries, novel technologies, or biomedical ...or environmental challenges, a fundamental understanding of science is necessary.
ABSTRACT
The impacts of science are felt across all socio-ecological levels, ranging from the individual to societal. In order to adapt or respond to scientific discoveries, novel technologies, or biomedical or environmental challenges, a fundamental understanding of science is necessary. However, antiscientific rhetoric, mistrust in science, and the dissemination of misinformation hinder the promotion of science as a necessary and beneficial component of our world. Scientists can promote scientific literacy by establishing dialogues with nonexperts, but they may find a lack of formal training as a barrier to public engagement. To address this, the American Society for Biochemistry and Molecular Biology (ASBMB) launched the Art of Science Communication course in 2015 in order to provide scientists at all career stages with introductory science communication training. In 2020, we conducted a retrospective survey of former participants to evaluate how the course had impacted participants’ science communication behaviors and their confidence engaging with nonexperts, as well as other benefits to their professional development. We found that scientists were significantly more likely to communicate with nonexpert audiences following the course compared to before (77% versus 51%;
P
< 0.0001). In addition, quantitative and qualitative data suggested that scientists were more confident in their ability to communicate science after completing the course (median of 8, standard deviation SD of 0.98 versus median of 5, SD of 1.57;
P
< 0.0001). Qualitative responses from participants supported quantitative findings. This suggested that the Art of Science Communication course is highly effective at improving the confidence of scientists to engage with the public and other nonexpert audiences regardless of career status. These data-driven perspectives provide a rationale for the implementation of broadly accessible science communication training programs that promote public engagement with science.
Numerous agencies (including ASBMB, ACS, IUBMB, NSF, and NIH) have called for formal ethics education in the undergraduate curriculum, yet there is widespread confusion over what this means, and ...therefore how to accomplish the task. Furthermore, while bioethics, animal rights, or medical ethics are rich fodder for discussion, the discussions are often polarizing, difficult to manage, and fail to achieve the desired outcomes (broadening the students understanding of ethics and ability to conduct science in line with a code of conduct). In this exercise, students read the novel Frankenstein by Mary Shelley and used the ethical situations in the novel as a launching off point for discussion of modern codes of conduct and ethical dilemmas. These include broader themes such as the responsibility of a creator to their creation, but also topics such as working safely in a laboratory, use of human subjects, and following an institutional code of conduct. Student discussions occurred in class in small groups (less than three students), class wide discussions (approximately 24 students) and in online forums through a closed Facebook group. Feedback from students was largely positive. Preliminary results indicate that this method is a viable way to broach sometimes difficult topics in scientific ethics from a safe distance and introduce professional codes of conduct and ethics to undergraduates.
This is from the Experimental Biology 2018 Meeting. There is no full text article associated with this published in The FASEB Journal.
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