Calcium-sensing Receptor and Keratinocyte Differentiation

Summary

Principal Investigator: Chia Ling Tu
Abstract: DESCRIPTION (provided by applicant): Epidermis consists of multiple layers of keratinocytes, which differentiate and produce a permeability barrier that provides protection against environmental insults. Extracellular calcium (Ca2+o) is essential for initiating keratinocyte differentiation and maintaining epidermal functions. Elevating Ca2+o concentration triggers an increase in the level of intracellular free Ca2+ (Ca2+i) and induces cell-cell adhesion, two key signaling events promoting keratinocyte differentiation. The increased Ca2+i level is due to Ca2+ release from internal stores and Ca2+ influx through channels in the plasma membrane. Raising Ca2+o also induces E-cadherin-mediated cell-cell adhesion by activating Rho A GTPase and Src/Fyn tyrosine kinase signaling pathways. The E-cadherin-mediated cell adhesion recruits and activates PI3K, an important regulator for cell survival and differentiation. The mechanisms transducing Ca2+o signals to cellular responses in keratinocytes have not been defined. The Ca2+-sensing receptor (CaR), a G-protein-coupled receptor, is expressed in keratinocytes. The CaR not only localizes on the cell membrane to detect changes in Ca2+o, but also forms a protein complex with modulators of Ca2+i stores and store-operated channels (SOC), including IP3R, PLC31 and a Ca2+-ATPase SPCA1 in the Golgi, which is a major Ca2+I reservoir in keratinocytes. Inhibition of CaR expression in vitro markedly suppresses Ca2+i responses to Ca2+o by reducing Ca2+i pools and blocks E-cadherin-mediated cell adhesion, leading to impaired cell differentiation. It is likely that the CaR conveys Ca2+o signals to activate downstream cellular responses by interacting with other signaling effectors such as G1, Rho guanine nucleotide exchange factor (RhoGEF) and filamin. To determine whether the CaR is responsible for sensing Ca2+o by keratinocytes in vivo, we generated keratinocyte-specific CaR knockout mice,EpidCaR-/-, by Cre-lox recombination. The epidermis of these mice manifest a loss of Ca2+ gradient, decreased production of lamellar bodies and cornified envelope, reduced expression of differentiation markers, and impaired permeability barrier functions. Keratinocytes from this mouse also display abnormal Ca2+I responses to Ca2+o and defective cell-cell adhesion. These data strongly support a role for the CaR in epidermal development. We will use this model and a well-established cell culture system to address the Hypothesis that the CaR mediates Ca2+o-induced keratinocyte differentiation by modulating Ca2+i signaling through direct interactions with molecules regulating Ca2+i stores and SOCs, and by promoting cell-cell adhesion via the activation of E-cadherin/PI3K pathway through Rho-dependent Src/Fyn signaling cascade. We propose the following Specific Aims: (1) to determine the role of CaR in mediating Ca2+o-induced differentiation and in regulating Ca2+i stores;(2) to determine the role of CaR in regulating E-cadherin-mediated cell-cell adhesion and activation of PI3K;(3) to determine the role of CaR- coupling proteins G1, RhoGEF and filamin A in Ca2+o-induced Ca2+i mobilization, E-cadherin-mediated cell-cell adhesion and keratinocyte differentiation. Our studies will greatly advance our knowledge of the Ca2+ signaling mechanisms that promote epidermal development and understanding of pathogenesis of skin disorders manifesting abnormal keratinocyte differentiation. PUBLIC HEALTH RELEVANCE: Ca2+ plays a critical role in controlling the growth, differentiation, and barrier function in skin cells by acting on a calcium-sensing receptor (CaR). This proposal will investigate how Ca2+ initiates skin cell differentiation and how the CaR mediates this process. Successful completion of this project will greatly advance our knowledge of skin cell differentiation and help understanding the pathogenesis of various skin disorders manifesting abnormal differentiation.
Funding Period: 2010-05-01 - 2015-02-28
more information: NIH RePORT

Top Publications

  1. pmc The calcium-sensing receptor-dependent regulation of cell-cell adhesion and keratinocyte differentiation requires Rho and filamin A
    Chia Ling Tu
    Endocrine Unit, Veteran Affairs Medical Center and University of California, San Francisco, California 94121, USA
    J Invest Dermatol 131:1119-28. 2011
  2. pmc Ablation of the calcium-sensing receptor in keratinocytes impairs epidermal differentiation and barrier function
    Chia Ling Tu
    Endocrine Unit, Veterans Affairs Medical Center, University of California, San Francisco, San Francisco, California 94121, USA
    J Invest Dermatol 132:2350-9. 2012
  3. pmc Sex and age modify biochemical and skeletal manifestations of chronic hyperparathyroidism by altering target organ responses to Ca2+ and parathyroid hormone in mice
    Zhiqiang Cheng
    Endocrine Research Unit, Department of Veterans Affairs Medical Center, Department of Medicine, University of California, San Francisco, CA, USA
    J Bone Miner Res 28:1087-100. 2013
  4. pmc Role of the calcium-sensing receptor in calcium regulation of epidermal differentiation and function
    Chia Ling Tu
    Endocrine Unit, Veterans Affair Medical Center and The University of California, San Francisco, CA, USA
    Best Pract Res Clin Endocrinol Metab 27:415-27. 2013
  5. pmc Obligatory roles of filamin A in E-cadherin-mediated cell-cell adhesion in epidermal keratinocytes
    Chia Ling Tu
    Endocrine Unit, Veteran Affairs Medical Center and University of California, San Francisco, CA, USA Electronic address
    J Dermatol Sci 73:142-51. 2014

Detail Information

Publications5

  1. pmc The calcium-sensing receptor-dependent regulation of cell-cell adhesion and keratinocyte differentiation requires Rho and filamin A
    Chia Ling Tu
    Endocrine Unit, Veteran Affairs Medical Center and University of California, San Francisco, California 94121, USA
    J Invest Dermatol 131:1119-28. 2011
    ..These results indicate that Rho is a downstream mediator of CaR in the regulation of Ca(2+)(o)-induced E-cadherin-mediated cell-cell adhesion and keratinocyte differentiation...
  2. pmc Ablation of the calcium-sensing receptor in keratinocytes impairs epidermal differentiation and barrier function
    Chia Ling Tu
    Endocrine Unit, Veterans Affairs Medical Center, University of California, San Francisco, San Francisco, California 94121, USA
    J Invest Dermatol 132:2350-9. 2012
    ..3%) diet. Deleting CaR perturbs the epidermal Ca(2+) gradient and impairs keratinocyte differentiation and permeability barrier homeostasis, indicating a key role for the CaR in normal epidermal development...
  3. pmc Sex and age modify biochemical and skeletal manifestations of chronic hyperparathyroidism by altering target organ responses to Ca2+ and parathyroid hormone in mice
    Zhiqiang Cheng
    Endocrine Research Unit, Department of Veterans Affairs Medical Center, Department of Medicine, University of California, San Francisco, CA, USA
    J Bone Miner Res 28:1087-100. 2013
    ..Restraining the ability of the PTG to upregulate CaSRs by heterozygous gene deletion contributes to biochemical and skeletal manifestations of HPT, especially in aging females...
  4. pmc Role of the calcium-sensing receptor in calcium regulation of epidermal differentiation and function
    Chia Ling Tu
    Endocrine Unit, Veterans Affair Medical Center and The University of California, San Francisco, CA, USA
    Best Pract Res Clin Endocrinol Metab 27:415-27. 2013
    ..The concepts derived from in vitro gene knockdown experiments have been evaluated and confirmed in three mouse models in vivo. ..
  5. pmc Obligatory roles of filamin A in E-cadherin-mediated cell-cell adhesion in epidermal keratinocytes
    Chia Ling Tu
    Endocrine Unit, Veteran Affairs Medical Center and University of California, San Francisco, CA, USA Electronic address
    J Dermatol Sci 73:142-51. 2014
    ..Filamin A has the ability to interact directly with CaR, Trio, and Rho and mediate CaR-dependent signaling events...

Research Grants30

  1. RAGE and Mechanisms of Vascular Dysfunction
    Shi Fang Yan; Fiscal Year: 2013
    ..Using novel and state-of-the-art techniques, floxed mice and molecular approaches to gene regulation, we are well-positioned to lead the study of RAGE in the next cycle of this Program. ..
  2. Role of Desmosomal Adhesion in Carcinogenesis
    MY GEORGIA MAHONEY; Fiscal Year: 2013
    ..Determining the molecular mechanisms by which desmoglein 2 affects tumor growth and development has the potential of identifying new targets for therapeutic cancer treatments. ..
  3. Cell Adhesion and Cytoskeletal Dynamics in Skin
    Elaine Fuchs; Fiscal Year: 2013
    ..This study is a fundamental prerequisite to understanding how aberrations in these basic properties go awry in skin cancers, including squamous cell carcinomas. ..
  4. TSH RECEPTOR MULTIMERIZATION
    TERRY FRANCIS DAVIES; Fiscal Year: 2013
    ....
  5. Internalization of gap junctions as a regulatory mechanism of direct GJIC
    Matthias M Falk; Fiscal Year: 2013
    ....
  6. Genetic and physiological mechanisms of temperature detection and compensation
    Piali Sengupta; Fiscal Year: 2013
    ..compensate for temperature fluctuations? 4) What defines the limits of the range in which these homeostatic mechanisms operate? 5) What are the common principles of temperature detection and compensation among species? ..
  7. AMPK Endothelial Cell Dysfunction and the Metabolic Syndrome (PROGRAM PROJECT)
    Neil B Ruderman; Fiscal Year: 2013
    ..The proposed studies should both yield novel insights into the biological bases for the premature atherosclerosis and impaired angiogenesis associated with this entity and suggest new therapeutic targets for their prevention...