The inner plasma membrane protein Plac8 regulates cell cycle progression in pancreatic ductal adenocarcinoma (PDAC)

Store-operated Ca2+entry (SOCE), mediated by the endoplasmic reticulum (ER) Ca2+sensor stromal interaction molecule 1 (STIM1) and the plasma membrane (PM) channel Orai1, is inhibited during mitosis. STIM1 phosphorylation has been suggested to mediate this inhibition, but it is unclear whether additional pathways are involved. Here, we demonstrate using various approaches, including a nonphosphorylatable STIM1 knock-in mouse, that STIM1 phosphorylation is not required for SOCE inhibition in mitosis. Rather, multiple pathways converge to inhibit Ca2+influx in mitosis. STIM1 interacts with the cochaperone BAG3 and localizes to autophagosomes in mitosis, and STIM1 protein levels are reduced. The density of ER–PM contact sites (CSs) is also dramatically reduced in mitosis, thus physically preventing STIM1 and Orai1 from interacting to activate SOCE. Our findings provide insights into ER–PM CS remodeling during mitosis and a mechanistic explanation of the inhibition of Ca2+influx that is required for cell cycle progression.

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Regulation of vascular smooth muscle cell proliferation by plasma membrane Ca(2+)-ATPase

AJP Cell Physiology ◽

10.1152/ajpcell.1997.272.6.c1947 ◽

1997 ◽

Vol 272 (6) ◽

pp. C1947-C1959 ◽

Cited By ~ 50

Author(s):

M. Husain ◽

L. Jiang ◽

V. See ◽

K. Bein ◽

M. Simons ◽

...

Keyword(s):

Cell Cycle ◽

Cell Proliferation ◽

Smooth Muscle ◽

Plasma Membrane ◽

Vascular Smooth Muscle ◽

Cell Cycle Progression ◽

Critical Role ◽

Cycle Progression ◽

Inhibit Cell Cycle Progression ◽

Transient Overexpression

We have previously shown that reductions in c-Myb-dependent transcription inhibit cell cycle progression and decrease intracellular Ca2+ concentrations in vascular smooth muscle cells (VSMC). We now report that these effects are largely mediated by a 4- to 10-fold increased rate of La(3+)-sensitive 45Ca extrusion, which is associated with 2- to 4-fold increased levels of plasma membrane Ca(2+)-ATPase 1 (PMCA1) mRNA and protein. PMCA4 mRNA, present at much lower concentrations, undergoes similar changes during suppression of c-Myb activity. We also report that PMCA1 expression is regulated during VSMC cell cycle progression, such that levels of PMCA1 are 40% lower at the G1/S interface than at G0. Moreover, transient overexpression of PMCA1a in VSMC elevates the 45Ca efflux rate by approximately 2-fold, decreases resting and peak thapsigargin-releasable Ca2+ concentrations at G1/S by 43% (68 nM) and 52% (160 nM), respectively, and reduces the rate of cell proliferation by over 2.5-fold. These data define a mechanism for c-Myb-dependent Ca2+ homeostasis and support a critical role for PMCA in the regulation of VSMC growth.

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Conserved Ark1-related kinases control TORC2 signaling

10.1101/870550 ◽

2019 ◽

Author(s):

Maria Alcaide-Gavilán ◽

Selene Banuelos ◽

Rafael Lucena ◽

Douglas R. Kellogg

Keyword(s):

Cell Cycle ◽

Growth Rate ◽

Plasma Membrane ◽

Cell Growth ◽

Cell Size ◽

Cell Cycle Progression ◽

Coordinated Control ◽

Cycle Progression ◽

Membrane Growth ◽

Slow Growing

AbstractIn all orders of life, cell cycle progression is dependent upon cell growth, and the extent of growth required for cell cycle progression is proportional to growth rate. Thus, cells growing rapidly in rich nutrients are substantially larger than slow growing cells. In budding yeast, a conserved signaling network surrounding Tor complex 2 (TORC2) controls growth rate and cell size in response to nutrient availability. Here, a search for new components of the TORC2 network identified a pair of redundant kinase paralogs called Ark1 and Prk1. Previous studies found that Ark/Prk play roles in endocytosis. Here, we show that Ark/Prk are embedded in the TORC2 network, where they appear to influence TORC2 signaling independently of their roles in endocytosis. We also show that reduced endocytosis leads to increased cell size, which indicates that cell size homeostasis requires coordinated control of plasma membrane growth and endocytosis. The discovery that Ark/Prk are embedded in the TORC2 network suggests a model in which TORC2-dependent signals control both plasma membrane growth and endocytosis, which would ensure that the rates of each process are matched to each other and to the availability of nutrients so that cells achieve and maintain an appropriate size.

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