About

Mitchel L. Villereal, PhD, is a Professor of Pharmacological and Physiological Sciences at the University of Chicago's Biological Sciences Division. His research focuses on cellular calcium signaling, particularly involving TRPC channels and store-operated calcium entry mechanisms. His work includes studying the translocation of TRPC6 channels into phagosomal membranes to augment phagosomal function, as well as investigating how calcium influx through store-operated channels influences processes relevant to neurodegenerative diseases such as Alzheimer’s disease. Dr. Villereal's research also explores the regulation of calcium channels by various modulators, including Stanniocalcin 2, tyrosine phosphatases, and cytochrome P450 activity. His contributions extend to understanding the molecular mechanisms of TRPC channel multimerization and the formation of native store-operated channels in human cells. His work has implications for cellular functions, immune responses, and neurophysiology, contributing to the broader understanding of calcium signaling pathways in health and disease.

Research topics

• Chemistry
• Cell biology
• Biology
• Biophysics
• Biochemistry

Selected publications

• TRPC6 channel translocation into phagosomal membrane augments phagosomal function

  Proceedings of the National Academy of Sciences · 2015-11-10 · 69 citations

  articleOpen access

  Defects in the innate immune system in the lung with attendant bacterial infections contribute to lung tissue damage, respiratory insufficiency, and ultimately death in the pathogenesis of cystic fibrosis (CF). Professional phagocytes, including alveolar macrophages (AMs), have specialized pathways that ensure efficient killing of pathogens in phagosomes. Phagosomal acidification facilitates the optimal functioning of degradative enzymes, ultimately contributing to bacterial killing. Generation of low organellar pH is primarily driven by the V-ATPases, proton pumps that use cytoplasmic ATP to load H(+) into the organelle. Critical to phagosomal acidification are various channels derived from the plasma membrane, including the anion channel cystic fibrosis transmembrane conductance regulator, which shunt the transmembrane potential generated by movement of protons. Here we show that the transient receptor potential canonical-6 (TRPC6) calcium-permeable channel in the AM also functions to shunt the transmembrane potential generated by proton pumping and is capable of restoring microbicidal function to compromised AMs in CF and enhancement of function in non-CF cells. TRPC6 channel activity is enhanced via translocation to the cell surface (and then ultimately to the phagosome during phagocytosis) in response to G-protein signaling activated by the small molecule (R)-roscovitine and its derivatives. These data show that enhancing vesicular insertion of the TRPC6 channel to the plasma membrane may represent a general mechanism for restoring phagosome activity in conditions, where it is lost or impaired.

  PublisherOA PDFDOI

• Possible role of the membrane potential in serum-stimulated uptake of amino acid in a diploid human fibroblast

  OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information) · 2014-06-27

  paratextOpen access1st authorCorresponding

  The Na/sup +/-dependent accumulation of ..cap alpha..-aminoisobutyric acid (AIB), measured in normal growing and quiescent (serum-derived) HSWP cells (human diploid fibroblast), was found to be 2-fold higher (AIB/sub in//AIB/sub out/ = 20 to 25) under normal growing conditions. Serum stimulation of quiescent cells increases their AIB concentrating capacity by approximately 70 percent within 1 hr. These observations suggest that the driving forces for AIB accumulation may be reversibly influenced by the serum concentration of the growth medium. Addition of valinomycin (Val) to cells pre-equilibrated with AIB causes an enhanced accumulation of AIB, suggesting that the membrane potential can serve as a driving force for AIB accumulation. After pre-equilibration with AIB in 6 mM K/sup +/, transition to 94 mM K/sup +/ with Val results in a marked and rapid net loss of AIB. The effect of Val on the accumulation of AIB is greatest in quiescent cells, with the intracellular AIB concentrations reaching those seen in both Val-stimulated, normal cells and Val-stimulated, serum-stimulated cells. By adjusting (K/sup +/)/sub 0/, in the presence of Val, the membrane potential of growing cells can be matched to that of quiescent cells or vice versa. The resultant AIB accumulating capacity is characteristic of the membrane potential rather than of the growth state. In summary, these data suggest that the accumulation of AIB in HSWP cells may be influenced by changes in membrane potential and that a serum-associated membrane hyperpolarization could be partly responsible for the increased capacity for AIB accumulation in serum-stimulated cells.

  Publisher

• Ca2+ Influx through Store-operated Ca2+ Channels Reduces Alzheimer Disease β-Amyloid Peptide Secretion

  Journal of Biological Chemistry · 2013-08-01 · 40 citations

  articleOpen access

  Alzheimer disease (AD), the leading cause of dementia, is characterized by the accumulation of β-amyloid peptides (Aβ) in senile plaques in the brains of affected patients. Many cellular mechanisms are thought to play important roles in the development and progression of AD. Several lines of evidence point to the dysregulation of Ca(2+) homeostasis as underlying aspects of AD pathogenesis. Moreover, direct roles in the regulation of Ca(2+) homeostasis have been demonstrated for proteins encoded by familial AD-linked genes such as PSEN1, PSEN2, and APP, as well as Aβ peptides. Whereas these studies support the hypothesis that disruption of Ca(2+) homeostasis contributes to AD, it is difficult to disentangle the effects of familial AD-linked genes on Aβ production from their effects on Ca(2+) homeostasis. Here, we developed a system in which cellular Ca(2+) homeostasis could be directly manipulated to study the effects on amyloid precursor protein metabolism and Aβ production. We overexpressed stromal interaction molecule 1 (STIM1) and Orai1, the components of the store-operated Ca(2+) entry pathway, to generate cells with constitutive and store depletion-induced Ca(2+) entry. We found striking effects of Ca(2+) entry induced by overexpression of the constitutively active STIM1(D76A) mutant on amyloid precursor protein metabolism. Specifically, constitutive activation of Ca(2+) entry by expression of STIM1(D76A) significantly reduced Aβ secretion. Our results suggest that disruptions in Ca(2+) homeostasis may influence AD pathogenesis directly through the modulation of Aβ production.

  PublisherOA PDFDOI

• Chronic exposure to stress hormones alters the subtype of store‐operated channels expressed in H19‐7 hippocampal neuronal cells

  Journal of Cellular Physiology · 2012-11-20 · 6 citations

  articleSenior authorCorresponding

  Differentiating H19-7 hippocampal precursor cells up-regulate (∼4.3-fold) store-operated channel (SOC) activity; relatively linear current-voltage curves indicate an I(SOC) subtype of SOC. In differentiated H19-7 neurons, the majority of agonist (arginine vasopressin, AVP)-stimulated Ca(2+) entry occurs via SOCs, based on 2-aminoethyldiphenylborinate (2-APB) inhibition data and the observation that transient receptor potential C1 (TRPC1) channel knock down cells show a dramatic reduction of thapsigargin-stimulated store-operated Ca(2+) entry (SOCE) and inhibition of AVP-stimulated Ca(2+) entry. Treatment of H19-7 cells with the rat stress hormone corticosterone during differentiation induces a significant increase in AVP-stimulated Ca(2+) entry, which is virtually eliminated by 2-APB, suggesting a corticosterone-induced increase of SOCE. Corticosterone also enhances AVP-stimulated Mn(2+) entry, confirming an elevated Ca(2+) entry pathway, rather than a decreased Ca(2+) extrusion. When corticosterone addition is delayed until after H19-7 cells have fully differentiated, it still elevates SOCE. In corticosterone-treated H19-7 cells, the knock down of TRPC1 no longer blocks thapsigargin-stimulated Ca(2+) entry suggesting that the subtype of SOCs expressed in H19-7 cells is altered by corticosterone treatment. Electrophysiological studies demonstrate that store-operated currents in corticosterone-treated H19-7 cells exhibit a highly inward rectifying current-voltage curve consistent with an I(CRAC) subtype of SOCs. Consistent with this finding is the observation that corticosterone treatment of H19-7 cells increases the expression of the I(CRAC) channel subunit Orai1. Thus, the subtype of SOCs expressed in H19-7 hippocampal neurons can be altered from I(SOC) to I(CRAC) by chronic treatment with stress hormones.

  PublisherDOI

• Stanniocalcin 2 Is a Negative Modulator of Store-Operated Calcium Entry

  Molecular and Cellular Biology · 2011-07-12 · 69 citations

  articleOpen access

  The regulation of cellular Ca(2+) homeostasis is essential for innumerable physiological and pathological processes. Stanniocalcin 1, a secreted glycoprotein hormone originally described in fish, is a well-established endocrine regulator of gill Ca(2+) uptake during hypercalcemia. While there are two mammalian Stanniocalcin homologs (STC1 and STC2), their precise molecular functions remain unknown. Notably, STC2 is a prosurvival component of the unfolded protein response. Here, we demonstrate a cell-intrinsic role for STC2 in the regulation of store-operated Ca(2+) entry (SOCE). Fibroblasts cultured from Stc2 knockout mice accumulate higher levels of cytosolic Ca(2+) following endoplasmic reticulum (ER) Ca(2+) store depletion, specifically due to an increase in extracellular Ca(2+) influx through store-operated Ca(2+) channels (SOC). The knockdown of STC2 expression in a hippocampal cell line also potentiates SOCE, and the overexpression of STC2 attenuates SOCE. Moreover, STC2 interacts with the ER Ca(2+) sensor STIM1, which activates SOCs following ER store depletion. These results define a novel molecular function for STC2 as a negative modulator of SOCE and provide the first direct evidence for the regulation of Ca(2+) homeostasis by mammalian STC2. Furthermore, our findings implicate the modulation of SOCE through STC2 expression as one of the prosurvival measures of the unfolded protein response.

  PublisherOA PDFDOI

• An increase in store-operated channel activity occurs during differentiation of hippocampal neurons

  The FASEB Journal · 2007-04-01

  article1st authorCorresponding
  Publisher

• Tyrosine phosphatase and cytochrome P450 activity are critical in regulating store-operated calcium channels in human fibroblasts

  Experimental & Molecular Medicine · 2006-12-01 · 8 citations

  articleOpen accessSenior author

  Diverse signaling pathways have been proposed to regulate store-operated calcium entry (SOCE) in a wide variety of cell types. However, it still needs to be determined if all of these known pathways operate in a single cell type. In this study, we examined involvement of various signaling molecules in SOCE using human fibroblast cells (HSWP). Bradykinin (BK)-stimulated Ca2+ entry, previously shown to be via SOCE, is enhanced by the addition of vanadate, an inhibitor of tyrosine phosphatases. Furthermore, SOCE is regulated by cytochrome P-450, as demonstrated by the fact that the products of cytochrome P-450 activity (14,15 EET) stimulated SOCE while econazole, an inhibitor of cytochrome P450, suppressed BK-stimulated Ca2+ entry. In contrast, Ca2+ entry was unaffected by the guanylate cyclase inhibitor LY83583, or the membrane permeant cyclic GMP analog 8-bromo-cyclic GMP (8-Br-cGMP). Neither nitric oxide donors nor phorbol esters affected BK-stimulated Ca2+ entry. SOCE in HSWP cells is primarily regulated by tyrosine phosphorylation and the cytochrome P-450 pathway, but not by cyclic GMP, nitric oxide, or protein kinase C. Thus, multiple pathways do operate in a single cell type leading to the activation of Ca2+ entry and some of these signaling pathways are more prominently involved in regulating calcium entry in different cell types.

  PublisherOA PDFDOI

• Mechanism and functional significance of TRPC channel multimerization

  Seminars in Cell and Developmental Biology · 2006-11-02 · 31 citations

  reviewOpen access1st authorCorresponding
  PublisherOA PDFDOI

• A new model for the activation of store‐operated channels

  The FASEB Journal · 2006-03-01

  article1st authorCorresponding

  Store‐operated channels (SOCs) are activated following depletion of intracellular Ca 2+ stores, however, the exact mechanism by which signals pass between endoplasmic reticulum (ER) Ca 2+ stores and plasma membrane SOCs is currently unknown. Previously, our laboratory demonstrated that tyrosine kinases are involved in the activation mechanism for SOCs. Here, we report that depletion of intracellular Ca 2+ stores by thapsigargin induces the transactivation of PDGF receptors (PDGFR‐β), and that this transactivation is necessary for the activation of SOCs. Furthermore, we demonstrate that store depletion leads to the tyrosine phosphorylation of two proposed SOC subunits, TRPC1 and TPRC3. Data is also provided to show that the transactivation of PDGFR‐β, following Ca 2+ store depletion, is blocked by expressing siRNA targeted to STIM1, the molecule that senses Ca 2+ levels in the ER stores. A novel model for the activation of SOCs is proposed by which store depletion acts via STIM1 to produce transactivation of the PDGFR signaling pathway resulting in the subsequent tyrosine phosphorylation of TRPC1 and TRPC3. To our knowledge, these findings are the first to demonstrate a link between STIM1 and a proposed signaling pathway for the activation of SOCs. This work was supported by NIGMS, NIH grant GM54500 (to M.L.V.).

  PublisherDOI

• Endogenous TRPC1, TRPC3, and TRPC7 Proteins Combine to Form Native Store-operated Channels in HEK-293 Cells

  Journal of Biological Chemistry · 2005-06-23 · 234 citations

  articleOpen accessSenior author

  Endogenously expressed canonical transient receptor potential (TRPC) homologs were investigated for their role in forming store-operated, 1-oleoyl-2-acetyl-sn-glycerol-stimulated, or carbachol (CCh)-stimulated calcium entry pathways in HEK-293 cells. Measurement of thapsigargin-stimulated Ba(2+) entry indicated that the individual suppression of TRPC1, TRPC3, or TRPC7 protein levels, by small interfering RNA (siRNA) techniques, dramatically inhibited (52-68%) store-operated calcium entry (SOCE), whereas suppression of TRPC4 or TRPC6 had no effect. Combined suppression of TRPC1-TRPC3, TRPC1-TRPC7, TRPC3-TRPC7, or TRPC1-TRPC3-TRPC7 gave only slightly more inhibition of SOCE (74-78%) than seen with suppression of TRPC1 alone (68%), suggesting that these three TRPC homologs work in tandem to mediate a large component of SOCE. Evidence from co-immunoprecipitation experiments indicates that a TRPC1-TRPC3-TRPC7 complex, predicted from siRNA results, does exist. The suppression of either TRPC3 or TRPC7, but not TRPC1, induced a high Ba(2+) leak flux that was inhibited by 2-APB and SKF96365, suggesting that the influx is via leaky store-operated channels. The high Ba(2+) leak flux is eliminated by co-suppression of TRPC1-TRPC3 or TRPC1-TRPC7. For 1-oleoyl-2-acetyl-sn-glycerol-stimulated cells, siRNA data indicate that TRPC1 plays no role in mediating Ba(2+) entry, which appears to be mediated by the participation of TRPC3, TRPC4, TRPC6, and TRPC7. CCh-stimulated Ba(2+) entry, on the other hand, could be inhibited by suppression of any of the five endogenously expressed TRPC homologs, with the degree of inhibition being consistent with CCh stimulation of both store-operated and receptor-operated channels. In summary, endogenous TRPC1, TRPC3, and TRPC7 participate in forming heteromeric store-operated channels, whereas TRPC3 and TRPC7 can also participate in forming heteromeric receptor-operated channels.

  PublisherDOI

Recent grants

• NIH Grant R01GM028359

  NIH · $1.9M · 1996

• NIH Grant R01GM054500

  NIH · $2.1M · 2005

• NIH Grant K04AM001182

  NIH · $53k · 1988

Frequent coauthors

• Charles Levinson

  21 shared

• Gordon A. Jamieson

  University of Cape Town

  9 shared

• Xiaoyan Wu

  South China Agricultural University

  8 shared

• Tatiana K. Zagranichnaya

  7 shared

• G. Babnigg

  Argonne National Laboratory

  6 shared

• N. E. Owen

  University of California, Davis

  6 shared

• Ruth D. Mayforth

  4 shared

• John S. Cook

  4 shared