Emerging roles of PtdIns(4,5)<i>P</i>2 – beyond the plasma membrane

Tan, Xiaojun; Thapa, Narendra; Choi, Sungyeol; Anderson, Richard A.

doi:10.1242/jcs.175208

Cited by 86 publications

(65 citation statements)

References 121 publications

(174 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…S3). The signaling lipid PI(4,5)P 2 has previously been detected on mitochondria (59), although at a much lower concentration than on the plasma membrane and in a sequestered form (59)(60)(61). We are not aware of any report showing PI4P on mitochondria.…”

Section: +mentioning

confidence: 80%

Investigations of human myosin VI targeting using optogenetically controlled cargo loading

French

Sosnick

Rock

2017

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

Myosins play countless critical roles in the cell, each requiring it to be activated at a specific location and time. To control myosin VI with this specificity, we created an optogenetic tool for activating myosin VI by fusing the light-sensitive Avena sativa phototropin1 LOV2 domain to a peptide from Dab2 (LOVDab), a myosin VI cargo protein. Our approach harnesses the native targeting and activation mechanism of myosin VI, allowing direct inferences on myosin VI function. LOVDab robustly recruits human full-length myosin VI to various organelles in vivo and hinders peroxisome motion in a lightcontrollable manner. LOVDab also activates myosin VI in an in vitro gliding filament assay. Our data suggest that protein and lipid cargoes cooperate to activate myosin VI, allowing myosin VI to integrate Ca 2+, lipid, and protein cargo signals in the cell to deploy in a site-specific manner.otor proteins play countless roles in biology, each requiring the motor to be recruited and activated at a particular time and place inside the cell. To dissect these multiple roles, we must develop tools that allow us to control the recruitment and activation process. One promising technique for achieving this goal is through optogenetics (1). Optogenetics involves the engineering and application of optically controlled, genetically encoded proteins and is transforming the fields of neuro-and cell biology (2, 3). A major benefit of optogenetics is that proteins are activated using light, which allows for high temporal and spatial control over a protein of interest.Myosin VI is a motor protein whose study could particularly benefit from optogenetic control. It is the only myosin known to walk toward the pointed end of actin filaments (4, 5). This property enables it to perform a diverse array of cellular functions, including cell division, endosome trafficking, autophagy, and Golgi and plasma membrane anchoring (6-9). Myosin VI is also autoinhibited, a property that is commonly found in other myosins (10). When myosin VI binds to cargo through specialized adaptor proteins, this autoinhibition is relieved through a poorly understood mechanism likely involving the disruption of an interaction between its cargo binding domain (CBD) and the myosin head (11,12). Dissociation of the CBD from the head both frees the head to bind tightly to actin and exposes dimerization sites throughout the tail domain of myosin VI, allowing it to become a processive dimer (13-15). In some cases, myosin VI could conceivably function as a monomer, for example when fulfilling its role as a membrane tether during spermatid individualization (16). If this is the case, more work is needed to elucidate the cellular signals that determine its oligomeric state at each site of action.Myosin VI has two classes of cargo proteins that bind to distinct, conserved motifs on the myosin VI C terminus (17). Disabled2, or Dab2, belongs to the class of cargo proteins that bind to a conserved WWY site on myosin (18). Optineurin (OPTN) is a member of the second class that binds ...

show abstract

Section: +mentioning

confidence: 80%

Investigations of human myosin VI targeting using optogenetically controlled cargo loading

French

Sosnick

Rock

2017

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

show abstract

“…Increasing evidence supports the specific and essential functions of intracellular PtdIns(4,5)P 2 (10). However, PtdIns(4,5)P 2 is poorly detected on intracellular compartments likely because of the lack of free PtdIns(4,5)P 2 , as it is bound to effectors that associate with PIP kinases (9).…”

Section: Discussionmentioning

confidence: 99%

“…PtdIns(4,5)P 2 plays multiple roles at the plasma membrane, such as in endocytosis, exocytosis, focal adhesion assembly, and so on (9). However, recently studies have argued for roles for PtdIns(4,5)P 2 at intracellular compartments (10). The majority of PtdIns(4,5)P 2 in mammalian cells are generated by the type I phosphatidylinositol 4-phosphate (PIP) 5-kinase (PIPKI), of which there are three genes (α, β, and γ) each with multiple splicing isoforms (11).…”

mentioning

confidence: 99%

PtdIns(4,5)P ₂ signaling regulates ATG14 and autophagy

Tan

Thapa

Liao

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

View full text Add to dashboard Cite

Autophagy is a regulated self-digestion pathway with fundamental roles in cell homeostasis and diseases. Autophagy is regulated by coordinated actions of a series of autophagy-related (ATG) proteins. The Barkor/ATG14(L)-VPS34 (a class III phosphatidylinositol 3-kinase) complex and its product phosphatidylinositol 3-phosphate [PtdIns(3)P] play key roles in autophagy initiation. ATG14 contains a C-terminal Barkor/ATG14(L) autophagosome-targeting sequence (BATS) domain that senses the curvature of PtdIns(3)P-containing membrane. The BATS domain also strongly binds PtdIns(4,5)P 2 , but the functional significance has been unclear. Here we show that ATG14 specifically interacts with type Iγ PIP kinase isoform 5 (PIPKIγi5), an enzyme that generates PtdIns(4,5)P 2 in mammalian cells. Autophagosomes have associated PIPKIγi5 and PtdIns(4,5)P 2 that are colocalized with late endosomes and the endoplasmic reticulum. PtdIns(4,5)P 2 generation at these sites requires PIPKIγi5. Loss of PIPKIγi5 results in a loss of ATG14, UV irradiation resistance-associated gene, and Beclin 1 and a block of autophagy. PtdIns(4,5)P 2 binding to the ATG14-BATS domain regulates ATG14 interaction with VPS34 and Beclin 1, and thus plays a key role in ATG14 complex assembly and autophagy initiation. This study identifies an unexpected role for PtdIns(4,5)P 2 signaling in the regulation of ATG14 complex and autophagy.M acroautophagy (referred to as autophagy from here on) is an intracellular self-digestion process conserved in all eukaryotes that maintains cell homeostasis and protects cells from various stresses. Autophagy involves the formation of doublemembrane autophagosomes that contain target cytoplasmic contents for lysosomal degradation (1). Autophagosome formation is driven by coordinated functions of a number of autophagy-related (ATG) proteins (2). The ATG14 (also called Barkor or ATG14L)-Beclin 1 (atg6 in yeast)-VPS34 (an enzyme involved in the cellular process of autophagy; class III PI3K) complex plays essential roles in the initiation steps of autophagy by generating phosphatidylinositol 3-phosphate [PtdIns(3)P] and recruiting PtdIns(3)P effectors (3-6). ATG14 functions by recruiting VPS34 to punctate structures associated with the endoplasmic reticulum (ER) (7), and then PtdIns(3)P, the product of VPS34, in turn binds the Barkor/Atg14 autophagosome targeting sequence (BATS) domain of ATG14 and regulates its membrane curvature sensing (8). The ATG14-BATS domain also binds PtdIns(4,5)P 2 without unknown functional relevance (8).Phosphoinositides are important lipid messengers in various membrane trafficking events. PtdIns(4,5)P 2 plays multiple roles at the plasma membrane, such as in endocytosis, exocytosis, focal adhesion assembly, and so on (9). However, recently studies have argued for roles for PtdIns(4,5)P 2 at intracellular compartments (10). The majority of PtdIns(4,5)P 2 in mammalian cells are generated by the type I phosphatidylinositol 4-phosphate (PIP) 5-kinase (PIPKI), of which there are three genes (α, β, and γ) each wit...

show abstract

“…Taken together, these data show that MSN can bind negatively charged lipids, including PIP2, suggesting that these interactions may contribute to MSN recruitment onto endosomal membranes. Indeed, PIP2 may be present not only at the plasma membrane but also on intracellular membranes, including early endosomes (Tan et al ., 2015). We conclude that MSN associates with specialized regions of early endosome membranes in a process that depends on negatively charged lipids but not on actin or ANXA2.…”

Section: Resultsmentioning

confidence: 99%