Regulation of glucose homeostasis by Doc2b and Munc18 proteins.

Indiana University-Purdue University Indianapolis (IUPUI)Glucose homeostasis is maintained through the coordinated actions of insulin secretion from pancreatic beta cells and insulin action in peripheral tissues. Dysfunction of insulin action yields insulin resistance, and when coupled with altered insulin secretion, results in type 2 diabetes (T2D). Exocytosis of intracellular vesicles, such as insulin granules and glucose transporter (GLUT4) vesicles is carried out by similar SNARE (soluble NSF attachment receptor) protein isoforms and Munc18 proteins. An additional regulatory protein, Doc2b, was implicated in the regulation of these particular exocytosis events in clonal cell lines, but relevance of Doc2b in the maintenance of whole body glucose homeostasis in vivo remained unknown. The objective of my doctoral work was to delineate the mechanisms underlying regulation of insulin secretion and glucose uptake by Doc2b in effort to identify new therapeutic targets within these processes for the prevention and/or treatment of T2D. Towards this, mice deficient in Doc2b (Doc2b-/- knockout mice) were assessed for in vivo alterations in glucose homeostasis. Doc2b knockout mice were highly susceptible to preclinical T2D, exhibiting significant whole-body glucose intolerance related to insulin secretion insufficiency as well as peripheral insulin resistance. These phenotypic defects were accounted for by defects in assembly of SNARE complexes. Having determined that Doc2b was required in the control over whole body glycemia in vivo, whether Doc2b is also limiting for these mechanisms in vivo was examined. To study this, novel Doc2b transgenic (Tg) mice were engineered to express ~3 fold more Doc2b exclusively in pancreas, skeletal muscle and fat tissues. Compared to normal littermate mice, Doc2b Tg mice had improved glucose tolerance, related to concurrent enhancements in insulin mumsecretion from beta cells and insulin-stimulated glucose uptake in the skeletal muscle. At the molecular level, Doc2b overexpression promoted SNARE complex assembly, increasing exocytotic capacities in both cellular processes. These results unveiled the concept that intentional elevation of Doc2b could provide a means of mitigating two primary aberrations underlying T2D development

Doc2b enrichment enhances glucose homeostasis in mice via potentiation of insulin secretion and peripheral insulin sensitivity.

AIMS/HYPOTHESIS: Insulin secretion from pancreatic beta cells and insulin-stimulated glucose uptake into skeletal muscle are processes regulated by similar isoforms of the soluble N-ethylmaleimide-sensitive factor-attachment protein receptor (SNARE) and mammalian homologue of unc-18 (Munc18) protein families. Double C2 domain β (Doc2b), a SNARE- and Munc18-interacting protein, is implicated as a crucial effector of glycaemic control. However, whether Doc2b is naturally limiting for these processes, and whether Doc2b enrichment might exert a beneficial effect upon glycaemia in vivo, remains undetermined. METHODS: Tetracycline-repressible transgenic (Tg) mice engineered to overexpress Doc2b simultaneously in the pancreas, skeletal muscle and adipose tissues were compared with wild-type (Wt) littermate mice regarding glucose and insulin tolerance, islet function in vivo and ex vivo, and skeletal muscle GLUT4 accumulation in transverse tubule/sarcolemmal surface membranes. SNARE complex formation was further assessed using Doc2b overexpressing L6-GLUT4-myc myoblasts to derive mechanisms relatable to physiological in vivo analyses. RESULTS: Doc2b Tg mice cleared glucose substantially faster than Wt mice, correlated with enhancements in both phases of insulin secretion and peripheral insulin sensitivity. Heightened peripheral insulin sensitivity correlated with elevated insulin-stimulated GLUT4 vesicle accumulation in cell surface membranes of Doc2b Tg mouse skeletal muscle. Mechanistic studies demonstrated Doc2b enrichment to enhance syntaxin-4-SNARE complex formation in skeletal muscle cells. CONCLUSIONS/INTERPRETATION: Doc2b is a limiting factor in SNARE exocytosis events pertinent to glycaemic regulation in vivo. Doc2b enrichment may provide a novel means to simultaneously boost islet and skeletal muscle function in vivo in the treatment and/or prevention of diabetes

Pride and prejudice of legal imperialism with reference to presevering English law in Malaysia: making sense the doctrines of reception and subsequent attraction

The benefit of the British Empire was that by the 18th Century, English Law was already well settled in the Malay Peninsular and it was relatively easy to determine which laws that can be received and applied. In light of the above, this chapter reviews the history of English law in Malay Peninsular with special focus on why the need to review ss. 3 and 5 of the Civil Law Act 1956, which relates to the current application of English Law in Malays

Pride and prejudice of legal imperialism and with reference to preserving English law in Malaysia: making sense of the doctrines of reception and subsequent attraction

A perusal of historical records of Penang, before the island was colonised by the East India Company, shows that the island was inhabited by some Malays and was already the playing ground of the Kedah royalties.6 Therefore, to argue that English law in Penang was ‘settled law’ would be inaccurate and contrary to the above established facts. Interestingly, the evolution of the law is seen during the British empire by taking on colonies and clearly it was to ensure that the heritage of the English law will live on and hence, making English law the law of the colony. The benefit of the British Empire was that by the 18th Century, English’s Law was already well settled in the Malay Peninsular and it was relatively easy to determine which laws that can be received and applied. In light of the above, this article reviews the history of English law in Malay Peninsular with special focus on why the need to review ss 3 and 5 of the Civil Law Act 1956,7 which relates to the current application of English Law in Malaysi

Future of legal education in Malaysia: towards a common bar course

The origins and the development of legal education and its profession in Malaysia lend its backdrop by the sponsors of the colonisation period in Malaysia.2 It is not known exactly when the legal profession was first introduced in England because prior to the 12th century3 the idea of courts generated from the local property ownership system where there were obligations of the people to the owners known as Lords which they occupied. Therefore, law and courts were practised according to the customary practises of the area or known as county.4 This shows that the legal profession per se at that time did not exist as how it is now practised

Mediation: religious and cultural disputes

Malaysia is a multi-ethnic and multi-religious country with Muslim, Hindus, Buddhists and Christians living together harmoniously. Its citizens are not only given freedom to practice their religious beliefs and cultures but are also thought to be tolerant and respectful to other religious beliefs and cultural practices.1 Undoubtedly, these values are vital for harmony to prevail in society and the country. Harmonious ties among the different races and cultures2 are necessary for the progress and betterment of the country. To touch on the sensitive aspects of another’s religious beliefs and cultural practices is in fact treading on dangerous ground

Doc2b serves as a scaffolding platform for concurrent binding of multiple Munc18 isoforms in pancreatic islet β-cells

Biphasic glucose-stimulated insulin secretion (GSIS) from pancreatic β-cells involves soluble N-ethylmaleimide-sensitive fusion protein-attachment protein receptor (SNARE) protein-regulated exocytosis. SNARE complex assembly further requires the regulatory proteins Munc18c, Munc18-1 and Doc2b. Munc18-1 and Munc18c are required for first- and second-phase GSIS respectively. These distinct Munc18-1 and Munc18c roles are related to their transient high-affinity binding with their cognate target (t-)SNAREs, Syntaxin 1A and Syntaxin 4 respectively. Doc2b is essential for both phases of GSIS, yet the molecular basis for this remains unresolved. Because Doc2b binds to Munc18-1 and Munc18c via its distinct C2A and C2B domains respectively, we hypothesized that Doc2b may provide a plasma membrane-localized scaffold/platform for transient docking of these Munc18 isoforms during GSIS. Towards this, macromolecular complexes composed of Munc18c, Doc2b and Munc18-1 were detected in β-cells. In vitro interaction assays indicated that Doc2b is required to bridge the interaction between Munc18c and Munc18-1 in the macromolecular complex; Munc18c and Munc18-1 failed to associate in the absence of Doc2b. Competition-based GST-Doc2b interaction assays revealed that Doc2b could simultaneously bind both Munc18-1 and Munc18c. Hence these data support a working model wherein Doc2b functions as a docking platform/scaffold for transient interactions with the multiple Munc18 isoforms operative in insulin release, promoting SNARE assembly

Munc18c: a controversial regulator of peripheral insulin action

Insulin resistance, a hallmark of impaired glucose tolerance and type 2 diabetes (T2D), arises from dysfunction of insulin action and subsequent glucose uptake by peripheral tissues, predominantly skeletal muscle and fat. Exocytosis of glucose transporter (GLUT4)-containing vesicles facilitated by soluble NSF (N-ethylmaleimide-sensitive factor) attachment receptor (SNARE) protein isoforms, and Munc18c (mammalian homolog of Unc-18c) mediates this glucose uptake. Emerging evidences, including recent human clinical studies, point to pivotal roles for Munc18c in peripheral insulin action in adipose and skeletal muscle. Intriguing new advances are also initiating debates regarding the molecular mechanism(s) controlling Munc18c action. The objective of this review is therefore to present a balanced perspective of new continuities and controversies surrounding the regulation and requirement for Munc18c in the regulation of peripheral insulin action

Constitutional oath of judges: a comparison with Australia, UK, US, and India

The written record of a judiciary oath can be traced as way back as ancient Greece, from Homer to Hesiod to Plate and it was more often than not associated with perjury . Hence oath was seen to be more closely related in law than religion. St Thomas Aquinas stated that “an oath is a reverence for the name of God is taken in confirmation of a promise. Hence what is confirmed by oath does not, for this reason, become an act of religio

The awakening of the dinosaurian Malaysian labour laws

The laws relating to employment are enacted to protect the rights of workers against exploitation by their employers. Although there are many laws regulating the relationship between an employee and employer in Malaysia, the focus of this article will be on the following two sources, the Employment Act 1955 (‘the EA 1955’)1 and the Industrial Relations Act 1967 (‘the IR 1967’).2 There are many reasons as to why employment law is very important and should be taken seriously. One of the many reasons are to prevent employees from being forced to overwork by employers. The EA 1955 provides inter alia, that employees should not exceed eight hours of work a day and should only work 48 hours in a week unless overtime wages are paid. Further, employees have to be given their fair amount of holidays and leaves as stated by the law. Without the EA 1955, employees may be forced to overwork which may cause many complications such as effects therefrom on their health. Furthermore, with the Children and Young Persons (Employment) Act 1966,3 the abuse of child labour can be prevented in this country. In this Act, a person aged below 14 years is categorised as child while a person above 14 and below 16, a young person. Children and young persons are only allowed to be employed in the family businesses that involve light work and do not require the use of machines. In the absence of these restrictions, there is high possibility that they may be exposed to exploitation which may lead to corruption