Plasma Membrane Ca2+-ATPase and Hair-Cell Function

Using lead citrate as a capture reagent and adenylate-(beta, gamma-methylene) diphosphate (AMP-PCP) as a substrate, we localized adenylate cyclase activity on the non-ruffled border plasma membrane of approximately half of the osteoclasts on trabecular bone surfaces in the tibial metaphyses of chickens fed a low (0.3%)-calcium diet. The enzyme was not detectable in osteoclasts when chickens were fed a normal calcium diet. Activity was observed on the entire plasma membrane of detached osteoclasts that were situated between osteoblasts on the bone surface and blood vessels in the marrow cavity. Detection of activity on detached osteoclasts required the presence of an activator, implying lower levels in these cells than in those with ruffled borders. Staining was greater on the lateral sides of osteoblasts and osteoclasts when they were in contact with each other. Reaction specificity was indicated by the demonstration of stimulation by forskolin, guanylate-(beta, gamma-methylene) diphosphate (GMP-PCP), dimethylsulfoxide, and NaF, inhibition by alloxan and 2',5'-dideoxyadenosine, and absence of activity when sections were incubated in substrate-free medium or when GMP-PCP replaced AMP-PCP as a substrate. The finding of adenylate cyclase in osteoclast plasma membrane provides structural evidence that the adenylate cyclase-cyclic AMP system has a role in regulation of osteoclast cell function. The low-calcium diet appears to have resulted in increased amounts of adenylate cyclase in osteoclasts.

Download Full-text

BACE2 plays a role in the insulin receptor trafficking in pancreatic β-cells

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.00420.2010 ◽

2010 ◽

Vol 299 (6) ◽

pp. E1087-E1095 ◽

Cited By ~ 22

Author(s):

Silvia Casas ◽

Paola Casini ◽

Sandra Piquer ◽

Jordi Altirriba ◽

Maud Soty ◽

...

Keyword(s):

Plasma Membrane ◽

Insulin Receptor ◽

Cell Function ◽

Coated Vesicles ◽

Amyloid Peptide ◽

Human Pancreas ◽

Β Cells ◽

Min6 Cells ◽

Β Cell Function ◽

Β Amyloid Peptide

BACE1 (β-site amyloidogenic cleavage of precursor protein-cleaving enzyme 1) is a β-secretase protein that plays a central role in the production of the β-amyloid peptide in the brain and is thought to be involved in the Alzheimer's pathogenesis. In type 2 diabetes, amyloid deposition within the pancreatic islets is a pathophysiological hallmark, making crucial the study in the pancreas of BACE1 and its homologous BACE2 to understand the pathological mechanisms of this disease. The objectives of the present study were to characterize the localization of BACE proteins in human pancreas and determine their function. High levels of BACE enzymatic activity were detected in human pancreas. In normal human pancreas, BACE1 was observed in endocrine as well as in exocrine pancreas, whereas BACE2 expression was restricted to β-cells. Intracellular analysis using immunofluorescence showed colocalization of BACE1 with insulin and BACE2 with clathrin-coated vesicles of the plasma membrane in MIN6 cells. When BACE1 and -2 were pharmacologically inhibited, BACE1 localization was not altered, whereas BACE2 content in clathrin-coated vesicles was increased. Insulin internalization rate was reduced, insulin receptor β-subunit (IRβ) expression was decreased at the plasma membrane and increased in the Golgi apparatus, and a significant reduction in insulin gene expression was detected. Similar results were obtained after specific BACE2 silencing in MIN6 cells. All these data point to a role for BACE2 in the IRβ trafficking and insulin signaling. In conclusion, BACE2 is hereby presented as an important enzyme in β-cell function.

Download Full-text

Proteomics Analysis of Plasma Membrane Fractions of the Root, Leaf, and Flower of Rice

International Journal of Molecular Sciences ◽

10.3390/ijms21196988 ◽

2020 ◽

Vol 21 (19) ◽

pp. 6988

Author(s):

Yukimoto Iwasaki ◽

Takafumi Itoh ◽

Yusuke Hagi ◽

Sakura Matsuta ◽

Aki Nishiyama ◽

...

Keyword(s):

Plasma Membrane ◽

Membrane Protein ◽

Plasma Membranes ◽

Cell Function ◽

Immunoblot Analysis ◽

Leaf Sheath ◽

Green Leaf ◽

Organ Specificity ◽

Plasma Membrane Protein ◽

Proteomics Data

The plasma membrane regulates biological processes such as ion transport, signal transduction, endocytosis, and cell differentiation/proliferation. To understand the functional characteristics and organ specificity of plasma membranes, plasma membrane protein fractions from rice root, etiolated leaf, green leaf, developing leaf sheath, and flower were analyzed by proteomics. Among the proteins identified, 511 were commonly accumulated in the five organs, whereas 270, 132, 359, 146, and 149 proteins were specifically accumulated in the root, etiolated leaf, green leaf, developing leaf sheath, and developing flower, respectively. The principle component analysis revealed that the functions of the plasma membrane in the root was different from those of green and etiolated leaves and that the plasma membrane protein composition of the leaf sheath was similar to that of the flower, but not that of the green leaf. Functional classification revealed that the root plasma membrane has more transport-related proteins than the leaf plasma membrane. Furthermore, the leaf sheath and flower plasma membranes were found to be richer in proteins involved in signaling and cell function than the green leaf plasma membrane. To validate the proteomics data, immunoblot analysis was carried out, focusing on four heterotrimeric G protein subunits, Gα, Gβ, Gγ1, and Gγ2. All subunits could be detected by both methods and, in particular, Gγ1 and Gγ2 required concentration by immunoprecipitation for mass spectrometry detection.

Download Full-text

Ion channels and transporters in cancer. 6. Vascularizing the tumor: TRP channels as molecular targets

AJP Cell Physiology ◽

10.1152/ajpcell.00280.2011 ◽

2012 ◽

Vol 302 (1) ◽

pp. C9-C15 ◽

Cited By ~ 35

Author(s):

Alessandra Fiorio Pla ◽

Daniele Avanzato ◽

Luca Munaron ◽

Indu S. Ambudkar

Keyword(s):

Endothelial Cells ◽

Plasma Membrane ◽

Transient Receptor Potential ◽

Cell Function ◽

Trp Channels ◽

In Vivo Studies ◽

Specific Reference ◽

Tumor Vascularization ◽

Extrinsic Factors ◽

Tumor Neovascularization

Tumor vascularization is a critical process that determines tumor growth and metastasis. In the last decade new experimental evidence obtained from in vitro and in vivo studies have challenged the classical angiogenesis model forcing us to consider new scenarios for tumor neovascularization. In particular, the genetic stability of tumor-derived endothelial cells (TECs) has been recently questioned in several studies, which show that TECs, as well as pericytes, differ significantly from their normal counterparts at genetic and functional levels. In addition to such an epigenetic action of tumor microenvironment on endothelial cells (ECs) commitment, the distinct characteristics of TECs could be due to differences in their origin compared with preexisting differentiated ECs. Intracellular Ca2+ signals are involved at different critical phases in the regulation of the complex process of angiogenesis and tumor progression. These signals are generated by a wide variety of intrinsic and extrinsic factors. Several key components of Ca2+ signaling including Ca2+ channels in the plasma membrane, endoplasmic reticulum, calcium pumps, and mitochondria contribute to the generation, amplitude, and frequency of these Ca2+ change. In particular, several members of the transient receptor potential (TRP) family of calcium-permeable channels have profound effects on the function of ECs. Because of its multifaceted role in the control of cell function, proliferation, and motility, TRP channels have been suggested as a potential molecular target for control of tumor neovascularization. Since plasma membrane Ca2+ channels are easily and directly accessible via the bloodstream, they are potential targets for a number of pharmacological and antibody-targeted therapeutic strategies, with specificity being the main limitation. In this review we discuss recent advances in understanding the role of Ca2+ channels, with specific reference to TRP channels, in tumor vascularization process.

Download Full-text

Auditory Brainstem Response Altered in Humans With Noise Exposure Despite Normal Outer Hair Cell Function

Ear and Hearing ◽

10.1097/aud.0000000000000370 ◽

2017 ◽

Vol 38 (1) ◽

pp. e1-e12 ◽

Cited By ~ 84

Author(s):

Naomi F. Bramhall ◽

Dawn Konrad-Martin ◽

Garnett P. McMillan ◽

Susan E. Griest

Keyword(s):

Hair Cell ◽

Auditory Brainstem Response ◽

Noise Exposure ◽

Outer Hair Cell ◽

Cell Function ◽

Auditory Brainstem ◽

Brainstem Response

Download Full-text

The genetics of hair-cell function in zebrafish

Journal of Neurogenetics ◽

10.1080/01677063.2017.1342246 ◽

2017 ◽

Vol 31 (3) ◽

pp. 102-112 ◽

Cited By ~ 26

Author(s):

Teresa Nicolson

Keyword(s):

Hair Cell ◽

Cell Function

Download Full-text

Adenylate cyclase 1 (ADCY1) mutations cause recessive hearing impairment in humans and defects in hair cell function and hearing in zebrafish

Human Molecular Genetics ◽

10.1093/hmg/ddu042 ◽

2014 ◽

Vol 23 (12) ◽

pp. 3289-3298 ◽

Cited By ~ 28

Author(s):

R. L. P. Santos-Cortez ◽

K. Lee ◽

A. P. Giese ◽

M. Ansar ◽

M. Amin-Ud-Din ◽

...

Keyword(s):

Adenylate Cyclase ◽

Hair Cell ◽

Hearing Impairment ◽

Cell Function

Download Full-text

Role of Na/Ca Exchange and the Plasma Membrane Ca2+-ATPase in beta Cell Function and Death

Annals of the New York Academy of Sciences ◽

10.1196/annals.1387.048 ◽

2007 ◽

Vol 1099 (1) ◽

pp. 456-467 ◽

Cited By ~ 32

Author(s):

A. HERCHUELZ ◽

A. KAMAGATE ◽

H. XIMENES ◽

F. VAN EYLEN

Keyword(s):

Plasma Membrane ◽

Beta Cell ◽

Beta Cell Function ◽

Cell Function

Download Full-text

Membrane recycling and epithelial cell function

AJP Renal Physiology ◽

10.1152/ajprenal.1989.256.1.f1 ◽

1989 ◽

Vol 256 (1) ◽

pp. F1-F12 ◽

Cited By ~ 14

Author(s):

D. Brown

Keyword(s):

Plasma Membrane ◽

Cell Function ◽

Collecting Duct ◽

Water Channel ◽

Cell Types ◽

Apical Plasma Membrane ◽

Proton Pumps ◽

Intercalated Cells ◽

Membrane Recycling ◽

Membrane Composition

The plasma membrane composition of virtually all eucaryotic cells is established, maintained, and modified by the process of membrane recycling. Specific plasma membrane components are inserted by exocytosis of transport vesicles, and are removed by endocytosis of segments of the membrane in which particular proteins are concentrated. In the kidney collecting duct, vasopressin induces the cycling of vesicles that are thought to carry water channels to and from the apical plasma membrane of principal cells, thus modulating the water permeability of this membrane. In the intercalated cells of the collecting duct, hydrogen ion secretion is controlled by the recycling of vesicles carrying proton pumps to and from the plasma membrane. In both cell types, "coated" carrier vesicles are involved, but whereas clathrin-coated vesicles participate in water channel recycling, the vesicles in intercalated cells are coated with the cytoplasmic domains of proton pumps. Following a brief outline of membrane recycling in general, this review summarizes previous data on membrane recycling in the collecting duct and related transporting epithelia and discusses some selected points relating to the role of membrane recycling and cell-specific function in the collecting duct.

Download Full-text