• Molecules and Cells
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• 제44권8호
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• pp.591-601
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• 2021

Cilia are highly specialized organelles that extend from the cell membrane and function as cellular signaling hubs. Thus, cilia formation and the trafficking of signaling molecules into cilia are essential cellular processes. TULP3 and Tubby (TUB) are members of the tubby-like protein (TULP) family that regulate the ciliary trafficking of G-protein coupled receptors, but the functions of the remaining TULPs (i.e., TULP1 and TULP2) remain unclear. Herein, we explore whether these four structurally similar TULPs share a molecular function in ciliary protein trafficking. We found that TULP3 and TUB, but not TULP1 or TULP2, can rescue the defective cilia formation observed in TULP3-knockout (KO) hTERT RPE-1 cells. TULP3 and TUB also fully rescue the defective ciliary localization of ARL13B, INPP5E, and GPR161 in TULP3 KO RPE-1 cells, while TULP1 and TULP2 only mediate partial rescues. Furthermore, loss of TULP3 results in abnormal IFT140 localization, which can be fully rescued by TUB and partially rescued by TULP1 and TULP2. TUB's capacity for binding IFT-A is essential for its role in cilia formation and ciliary protein trafficking in RPE-1 cells, whereas its capacity for PIP₂ binding is required for proper cilia length and IFT140 localization. Finally, chimeric TULP1 containing the IFT-A binding domain of TULP3 fully rescues ciliary protein trafficking, but not cilia formation. Together, these two TULP domains play distinct roles in ciliary protein trafficking but are insufficient for cilia formation in RPE-1 cells. In addition, TULP1 and TULP2 play other unknown molecular roles that should be addressed in the future.

• The Korean Journal of Physiology and Pharmacology
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• 제25권6호
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• pp.593-601
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• 2021

Primary cilia on kidney tubular cells play crucial roles in maintaining structure and physiological function. Emerging evidence indicates that the absence of primary cilia, and their length, are associated with kidney diseases. The length of primary cilia in kidney tubular epithelial cells depends, at least in part, on oxidative stress and extracellular signal-regulated kinase 1/2 (ERK) activation. Hydrogen sulfide (H₂S) is involved in antioxidant systems and the ERK signaling pathway. Therefore, in this study, we investigated the role of H₂S in primary cilia elongation and the downstream pathway. In cultured Madin-Darby Canine Kidney cells, the length of primary cilia gradually increased up to 4 days after the cells were grown to confluent monolayers. In addition, the expression of H₂S-producing enzyme increased concomitantly with primary cilia length. Treatment with NaHS, an exogenous H₂S donor, accelerated the elongation of primary cilia whereas DL-propargylglycine (a cystathionine γ-lyase inhibitor) and hydroxylamine (a cystathionine-β-synthase inhibitor) delayed their elongation. NaHS treatment increased ERK activation and Sec10 and Arl13b protein expression, both of which are involved in cilia formation and elongation. Treatment with U0126, an ERK inhibitor, delayed elongation of primary cilia and blocked the effect of NaHS-mediated primary cilia elongation and Sec10 and Arl13b upregulation. Finally, we also found that H₂S accelerated primary cilia elongation after ischemic kidney injury. These results indicate that H₂S lengthens primary cilia through ERK activation and a consequent increase in Sec10 and Arl13b expression, suggesting that H₂S and its downstream targets could be novel molecular targets for regulating primary cilia.

• Molecules and Cells
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• 제45권4호
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• pp.169-176
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• 2022

A primary cilium, a hair-like protrusion of the plasma membrane, is a pivotal organelle for sensing external environmental signals and transducing intracellular signaling. An interesting linkage between cilia and obesity has been revealed by studies of the human genetic ciliopathies Bardet-Biedl syndrome and Alström syndrome, in which obesity is a principal manifestation. Mouse models of cell type-specific cilia dysgenesis have subsequently demonstrated that ciliary defects restricted to specific hypothalamic neurons are sufficient to induce obesity and hyperphagia. A potential mechanism underlying hypothalamic neuron cilia-related obesity is impaired ciliary localization of G protein-coupled receptors involved in the regulation of appetite and energy metabolism. A well-studied example of this is melanocortin 4 receptor (MC4R), mutations in which are the most common cause of human monogenic obesity. In the paraventricular hypothalamus neurons, a blockade of ciliary trafficking of MC4R as well as its downstream ciliary signaling leads to hyperphagia and weight gain. Another potential mechanism is reduced leptin signaling in hypothalamic neurons with defective cilia. Leptin receptors traffic to the periciliary area upon leptin stimulation. Moreover, defects in cilia formation hamper leptin signaling and actions in both developing and differentiated hypothalamic neurons. The list of obesity-linked ciliary proteins is expending and this supports a tight association between cilia and obesity. This article provides a brief review on the mechanism of how ciliary defects in hypothalamic neurons facilitate obesity.

• BMB Reports
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• 제46권2호
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• pp.73-79
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• 2013

Polycystic kidney disease (PKD) is a common hereditary disorder which is characterized by fluid-filled cysts in the kidney. Mutation in either PKD1, encoding polycystin-1 (PC1), or PKD2, encoding polycystin-2 (PC2), are causative genes of PKD. Recent studies indicate that renal cilia, known as mechanosensors, detecting flow stimulation through renal tubules, have a critical function in maintaining homeostasis of renal epithelial cells. Because most proteins related to PKD are localized to renal cilia or have a function in ciliogenesis. PC1/PC2 heterodimer is localized to the cilia, playing a role in calcium channels. Also, disruptions of ciliary proteins, except for PC1 and PC2, could be involved in the induction of polycystic kidney disease. Based on these findings, various PKD mice models were produced to understand the roles of primary cilia defects in renal cyst formation. In this review, we will describe the general role of cilia in renal epithelial cells, and the relationship between ciliary defects and PKD. We also discuss mouse models of PKD related to ciliary defects based on recent studies.

• Biomolecules & Therapeutics
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• 제23권4호
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• pp.327-332
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• 2015

Primary cilia have critical roles in coordinating multiple cellular signaling pathways. Dysregulation of primary cilia is implicated in various ciliopathies. To identify specific regulators of autophagy, we screened chemical libraries and identified mefloquine, an anti-malaria medicine, as a potent regulator of primary cilia in human retinal pigmented epithelial (RPE) cells. Not only ciliated cells but also primary cilium length was increased in mefloquine-treated RPE cells. Treatment with mefloquine strongly induced the elongation of primary cilia by blocking disassembly of primary cilium. In addition, we found that autophagy was increased in mefloquine-treated cells by enhancing autophagic flux. Both chemical and genetic inhibition of autophagy suppressed ciliogenesis in mefloquine-treated RPE cells. Taken together, these results suggest that autophagy induced by mefloquine positively regulates the elongation of primary cilia in RPE cells.

• Biomolecules & Therapeutics
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• 제30권2호
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• pp.170-178
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• 2022

The airway epithelium is equipped with the ability to resist respiratory disease development and airway damage, including the migration of airway epithelial cells and the activation of TLR3, which recognizes double-stranded (ds) RNA. Primary cilia on airway epithelial cells are involved in the cell cycle and cell differentiation and repair. In this study, we used Beas-2B human bronchial epithelial cells to investigate the effects of the TLR3 agonist polyinosinic:polycytidylic acid [Poly(I:C)] on airway cell migration and primary cilia (PC) formation. PC formation increased in cells incubated under serum deprivation. Migration was faster in Beas-2B cells pretreated with Poly(I:C) than in control cells, as judged by a wound healing assay, single-cell path tracking, and a Transwell migration assay. No changes in cell migration were observed when the cells were incubated in conditioned medium from Poly(I:C)-treated cells. PC formation was enhanced by Poly(I:C) treatment, but was reduced when the cells were exposed to the ciliogenesis inhibitor ciliobrevin A (CilioA). The inhibition of Beas-2B cell migration by CilioA was also assessed and a slight decrease in ciliogenesis was detected in SARS-CoV-2 spike protein (SP)-treated Beas-2B cells overexpressing ACE2 compared to control cells. Cell migration was decreased by SP but restored by Poly(I:C) treatment. Taken together, our results demonstrate that impaired migration by SP-treated cells can be attenuated by Poly(I:C) treatment, thus increasing airway cell migration through the regulation of ciliogenesis.

• BMB Reports
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• 제52권10호
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• pp.619-624
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• 2019

The primary cilium is a microtubule-based structure projecting from a cell. Although the primary cilium shows no motility, it can recognize environmental stimuli. Thus, ciliary defects cause severe abnormalities called ciliopathies. Ciliogenesis is a very complex process and involves a myriad of components and regulators. In order to excavate the novel positive regulators of ciliogenesis, we performed mRNA microarray using starved NIH/3T3 cells. We selected 62 murine genes with corresponding human orthologs, with significantly upregulated expression at 24 h after serum withdrawal. Finally, calpain-6 was selected as a positive regulator of ciliogenesis. We found that calpain-6 deficiency reduced the percentage of ciliated cells and impaired sonic hedgehog signaling. It has been speculated that this defect might be associated with decreased levels of ${\alpha}-tubulin$ acetylation at lysine 40. This is the first study to report a novel role of calpain-6 in the formation of primary cilia.

• 대한수의학회지
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• 제22권2호
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• pp.99-109
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• 1982

Morphological changes of the oviductal epithelium of the rat treated with hormones ($17{\beta}$-estradiol ${\mu}g$/day and progesterone 2.5mg/day) for ten days were observed transmission and scanning electron microscopically. The results obtained were as follows: 1. The cilia formation of ciliary cell(CC) was more accelerated by the treatment of estradiol than progesterone, but the balance of estrogen and progesterone was required for the maintenance of CC. The effect of hormone was different between the segments for the maintenance of CC. 2. The short secretory cell(SSC) was severely inhibited in the formation of secretory granules with single hormonal treatment but the activity of secretion was more inhibited by progesterone than by estradiol. 3. The long secretory cell(LSC) had not a great difference between estradiol and progesterone treatments as compared with the normal sexual cycle, but the formation of secretory granules was somewhat accelerated by progesterone treatment. 4. The formation of secretory granules of junctional cell (JC) was severely accelerated by estradiol treatment as compared with the normal sexual cycle. The formation of secretory granules during progesterone treatment, on the other hand, was inhibited completely, but the numbers of pinocytotic vesicles appeared at the cytoplasmic apical portion. 5. Three types of secretory cells, SSC, LSC and JC, on the rat oviductal epithelium could be suggested to have different cell tapes respectively from the morphological changes by hormone treatment.

• 대한화장품학회지
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• 제44권1호
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• pp.73-79
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• 2018

일차 섬모(primary cilia)는 세포에서 안테나처럼 돌출되어 나온 기관인데, 외부 자극에 반응할 수 있는 각종 수용체와 채널, 신호 전달 인자들을 가지고 있다. 피부는 자외선, 온도, 습도, 중력, 장력 등 외부 환경에 반응하여 멜라닌이나 콜라겐을 만들고 피부 장벽을 형성한다. 피부에서는 일차 섬모가 없으면 헤어의 생성이나 각질의 분화가 억제된다는 보고가 있다. 또한 피부 색소 생성과 관련하여서는 일차 섬모가 sonic hedgehog-smoothened-GLI2 신호 전달에 의해 활성화되면 멜라닌 생성이 억제된다는 것이 알려져 있다. 피부가 자외선을 받으면 멜라닌 생성 호르몬의 양이 증가하고 멜라닌 생성 호르몬은 멜라닌 생성 세포 내 cAMP의 양을 증가시켜 멜라닌 생성 효소의 발현을 높인다. 이에 멜라닌 생성 호르몬과 세포 내 cAMP의 양을 증가시키는 물질을 처리하여 멜라닌 생성을 높였을 때 일차 섬모의 변화를 확인한 결과 일차 섬모가 감소하는 것을 확인하였다. 또한 기존 미백 원료인 유용성 감초 추출물(an ethanol extract of Glycyrrhiza glabra (EGG) root)과 Melasolv (3,4,5-trimethoxy cinnamate thymol ester (TCTE))가 일차 섬모의 발현을 증가시키고 멜라닌 생성 효소인 tyrosinase의 발현을 억제함을 확인할 수 있었다. 따라서 일차 섬모를 조절할 수 있다면 피부 색소 침착을 효과적으로 조절할 수 있을 것이다.

• 한국패류학회지
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• 제27권3호
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• pp.213-221
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• 2011

TBTCl에 36주 동안 노출된 대복, Gomphina veneriformis 의 미세구조적인 변화를 전자현미경으로 관찰하였다. 대복의 외투막은 가장자리에 4개의 주름을 가지며, 내부와 외부상피층이 단층의 원주형 상피세포, 섬모세포, 분비세포로 구성되어 있었다. 이들 상피층은 혈림프동이 존재하는 결합조직층을 둘러싸고 있었다. 대복의 외투막은 TBTCl 노출 12주째 내부상피층에 존재하는 섬모의 수가 감소하였으며, 혈림프동의 확장과 함께 격막의 파괴가 관찰되었다. 노출 20주째 세포질내의 공포형성, 핵응축과 같은 변화가 관찰되었고, 결합조직층에서는 근섬유다발의 분절이 부분적으로 관찰되었다. 노출 28주째 상피층의 부분적인 붕괴, 섬모의 변화 및 섬모세포에 존재하는 미세구조가 괴사되었다. 결합조직층에 존재하는 다수의 근형질막은 팽창되었으며, 막의 내부에는 근섬유들이 대부분 파괴되어 막 주변에 근섬유 잔여물들이 관찰되었다. 노출 36주째에는 섬모들은 모두 탈락되고, 핵 응축되고, 이형소체의 증가가 나타나는 퇴행성 상피세포가 나타났다. 외부상피층의 상피세포들이 괴상되어 핵이 파괴되고, 세포질 내에는 다수의 용해소체들이 가득 차 있었으며, 미세융모들은 대부분 소실되었다. 따라서 만성적인 TBTCl 노출은 대복의 외투막은 각장성장 및 생리적인 기능의 장애를 유발하는 것으로 생각된다.