The Mechanosensitive Pkd2 Channel Modulates the Recruitment of Myosin II and Actin to the Cytokinetic Contractile Ring.

Cytokinesis, the last step in cell division, separates daughter cells through mechanical force. This is often through the force produced by an actomyosin contractile ring. In fission yeast cells, the ring helps recruit a mechanosensitive ion channel, Pkd2, to the cleavage furrow, whose activation by membrane tension promotes calcium influx and daughter cell separation. However, it is unclear how the activities of Pkd2 may affect the actomyosin ring. Here, through both microscopic and genetic analyses of a hypomorphic pkd2 mutant, we examined the potential role of this essential gene in assembling the contractile ring. The pkd2-81KD mutation significantly increased the counts of the type II myosin heavy chain Myo2 (+18%), its regulatory light chain Rlc1 (+37%) and actin (+100%) molecules in the ring, compared to the wild type. Consistent with a regulatory role of Pkd2 in the ring assembly, we identified a strong negative genetic interaction between pkd2-81KD and the temperature-sensitive mutant myo2-E1. The pkd2-81KD myo2-E1 cells often failed to assemble a complete contractile ring. We conclude that Pkd2 modulates the recruitment of type II myosin and actin to the contractile ring, suggesting a novel calcium-dependent mechanism regulating the actin cytoskeletal structures during cytokinesis.

The mechanosensitive Pkd2 channel modulates the recruitment of myosin II and actin to the cytokinetic contractile ring.

Cytokinesis, the last step in cell division, separate daughter cells through the force produced by an actomyosin contractile ring assembled at the equatorial plane. In fission yeast cells, the ring helps recruit a mechanosensitive ion channel Pkd2 to the cleavage furrow, whose activation by membrane tension promotes calcium influx and daughter cell separation. However, it is unclear how the activities of Pkd2 may affect the actomyosin ring. Here, through both microscopic and genetic analyses of a hypomorphic mutant of the essential pkd2 gene, we examine its potential role in assembling and constricting the contractile ring. The pkd2-81KD mutation significantly increased the number of type II myosin heavy chain Myo2 (+20%), its regulatory light chain Rlc1 (+37%) and actin (+20%) molecules in the ring, compared to the wild type. Consistent with a regulatory role of Pkd2 in the ring assembly, we identified a strong negative genetic interaction between pkd2-81KD and the temperature-sensitive mutant myo2-E1 . The pkd2-81KD myo2-E1 cells often failed to assemble a complete contractile ring. We conclude that Pkd2 modulates the recruitment of type II myosin and actin to the contractile ring, suggesting a novel calcium- dependent mechanism regulating the actin cytoskeletal structures during cytokinesis.

The cytoplasmic tail of the mechanosensitive channel Pkd2 regulates its internalization and clustering in eisosomes.

Polycystins are a family of conserved ion channels, mutations of which lead to one of the most common human genetic disorders, namely, autosomal dominant polycystic kidney disease. Schizosacchromyces pombe possesses an essential polycystin homologue, Pkd2, which directs Ca2+ influx on the cell surface in response to membrane tension, but its structure remains unsolved. Here, we analyzed the structure-function relationship of Pkd2 based on its AlphaFold-predicted structure. Pkd2 consists of three domains, the extracellular lipid-binding domain (LBD), nine-helix transmembrane domain (TMD) and C-terminal cytoplasmic domain (CCD). Our genetic and microscopy data revealed that LBD and TMD are essential for targeting Pkd2 to the plasma membrane from the endoplasmic reticulum. In comparison, CCD ensures the polarized distribution of Pkd2 by promoting its internalization and preventing its clustering in the eisosome, a caveolae-like membrane compartment. The domains of Pkd2 and their functions are conserved in other fission yeast species. We conclude that both extracellular and cytoplasmic domains of Pkd2 are crucial for its intracellular trafficking and function. We propose that mechanosensitive channels can be desensitized through either internalization or clustering in low-tension membrane compartments.

Barriers to treatment regimen adherence in Indian women with polycystic ovarian syndrome.

Background: Polycystic ovarian syndrome (PCOS) is a hormonal disorder that affects women of the reproductive age group. Its treatment regimen comprises medication and lifestyle modifications. However, non-adherence to the treatment regimen is the most commonly faced problem among women due to various barriers, resulting in complications like insulin resistance, hyperlipidemia, obesity, and infertility. Primary care physicians see patients with this disorder either at the initiation of treatment or on follow-up care after specialist consultation. So, understanding the barriers to treatment compliance, from a woman's perspective and finding the solution to the same is crucial to successful therapy. Objectives: The present study aims to assess adherence to the treatment regimen and its barriers among women with PCOS and its associated factors. Methods: A cross-sectional study among 224 women who met the inclusion criteria responded through a Google form. Self-reports were obtained by a demographic proforma, medication adherence rating scale, and barriers assessment questionnaire. Results: Only a third of the women (32.1%) were fully adherent, 36.3% were partially adherent, and 31.6% were non-adherent. The most common barriers among women were lack of knowledge regarding the disease and its management, side effects of the treatment, long duration of the therapy, no relief of symptoms, bland diet, and lack of physical exercise. Treatment adherence was associated with socioeconomic status (P = 0.001) among women with PCOS. Conclusion: Adherence to the treatment regimen in PCOS was poor. Successful adherence depends on how patients understand the severe implications of non-adherence to the prescribed treatment and adjust to lifestyle modifications related barriers. It is also vital for health care providers and patients to identify these barriers, address them and refine treatment strategies.

Expression of ß-catenin in oral leukoplakia and oral submucous fibrosis: An immunohistochemical study.

BACKGROUND: Oral potentially malignant disorders have increased propensity to turn malignant than its apparently normal counterparts. Histopathological examination, although gold standard, needs adjunct technique to give accurate diagnosis. Immunohistochemistry has proved to be a promising adjunct to aid in the diagnosis so far. The quest for a definitive marker is still on. Beta-catenin (ß-catenin), a structural protein has been evaluated to identify its likely role in malignant transformation of potentially malignant lesions and possibly designate it as one of the identifiable signature molecules in the transformation. AIM AND OBJECTIVE: To evaluate and estimate the expression of ß-catenin in different grades of dysplasia, oral submucous fibrosis (OSMF) and normal mucosa and compare the same. METHODOLOGY: A total number of 40 cases including different grades of dysplasia, OSMF and normal mucosa were immunohistochemically stained, location and intensity of its expression were evaluated for ß-catenin. The results were statistically analyzed using the one-way analysis of variance and Chi-square test. RESULTS: The expression of ß-Catenin in the cytoplasm as well as in the nucleus increased from mild-to-moderate dysplasia to OSMF and to severe epithelial dysplasia in an increasing order. The expression is seen to translocate from membranous to cytoplasm to nucleus indicating a proliferative potential in these group of lesions. CONCLUSION: ß-catenin is a promising marker which indicates the malignant transformation potential in the higher grades of dysplasia and OSMF.

Estimation of expression of beta-human chorionic gonadotropin levels through progression of disease from normal to epithelial dysplasia to malignancy.

BACKGROUND: Gonadotropins have been extensively studied in trophoblastic and nontrophoblastic tumors of breast, gastric, bladder, parathyroid, renal cell and cervical carcinomas, with a significant increase in tissue expressions. Serum levels of beta-human chorionic gonadotropin (ß-hCG) and its tissue expression were found more in oral squamous cell carcinoma (OSCC) patients with a significant diagnostic and prognostic value. No such study has been done on oral epithelial dysplasia (OED). AIMS AND OBJECTIVE: To evaluate the expression of ß-hCG in OED and the feasibility of using this marker for early diagnosis and to see its progression from normal to dysplasia to malignancy. MATERIALS AND METHODS: The study population consisted of thirty histologically confirmed cases of OED and thirty cases of OSCC. Fifteen normal tissues were also included in the study. All the tissue samples were subjected to immunohistochemical (IHC) staining using antimouse ß-hCG antibody. RESULTS: The IHC expression of ß-hCG was completely negative in normal cases (Group 1 [n = 15]), whereas 13 (43.3%) cases of OED (Group 2 [n = 30]) and 13 cases (43.3%) of OSCC (Group 3 [n = 30]) showed diffuse cytoplasmic staining in dysplastic surface epithelium and epithelial islands of OSCC. This difference was statistically significant with P = 0.007. CONCLUSION: We conclude that the expression of ß-hCG increased from normal mucosa to dysplasia to OSCC, suggesting that it is involved in the early stage of carcinogenesis and progression of the disease.