Week 6 Flashcards
What regulates cell proliferation?
- Nutrient status; ENTOR highly associated w/ nutrient status
- Epigenetics can control whether or not genes will be expressed: Proto-onco genes normal genes that when acquire mutation become onco gene
- Status of DNA: Protien that monitors this: p53; Transcription factor that can interact w/ p21; Need CDK to go to cell cycle and needs to interact w/ cyclins
- Growth factor signaling thru RTK
- Contact inhibition by other cells or those cells can even proliferate them
- Apoptotic cascade suppressed by BCL2; Pro apoptotic: BAX and BAC trigger cytochrome C
Contact inhibtion
- occurs with E cadherin and the extracellular matrix
Growth factors from ECM
- cell surface integrins interact with cytoskeleton at focal adhesion complexes which can initiate production of intracellular messengers or directly transduce signals to the nucleus
- FAK: focal adhesion kinase;
- SRC: tyrosine kinase
- Activated and inactivated by phosphorylation
- Important because extracellular environment can control what happens in intracellular environment by activating integrins which will activate other cascades down the line
How does extracellular environment signal nucleus to transcribe proteins for growth?
-ligand binds to receptor, auto cross phosphorylation which causes phosphorylation of signaling protein that initiates phosphorylation of other proteins to cause DNA to make proteins that will induce cell growth/replication
TGF beta arresting cell division
- TGF beta binds to TGF beta receptor which activates the receptors intracellular protein kinase domain leading to phosphorylation of SMAD protiens which will then enter nucleus and bind to promoters of genes that control transcription
- key target is p21 gene which will inhibit cyclinE/-cdk2 complex to lead to cell arrest
4 types of receptors
- Ligand gated ion channels
- G protein coupled receptors
- Enzyme linked receptors
- Nuclear receptors
G protein coupled receptors
- activate Heterotrimeric g proteins and Alpha subunit ( either stimulatory or inhibitory or phsophorylates)
- specificity is controlled by controlling which g protein sub-unit is activated
- cell response is determined by extracellular signaling
Enzyme linked receptors
- when activated it turns on other enzymes
- Can be receptors that have tyrosine kinase activity or associated with tyrosine kinase
Nuclear receptors
- steroid receptors
- Located in nucleus or cytoplasm
- Signal diffuses across the membrane b/c they are hydrophobic
JAK/STAT pathway
- cytokine receptor
- cytokine binds to JAK receptor
- JAK auto-phosphorylates
- STAT binds to auto-phosphorylated JAK
- JAK phosphorylates STAT
- STAT dimer forms, travels to nucleus binds DNA and changes gene expression
How do the same pathways lead to different outcomes?
- regulation at different points in the pathways
- different receptors: which depends on what kind of cell it is
- different signaling cascades from the same receptors
- local signaling domains within the cytoplasm
How do heterotrimeric G proteins differ in signaling targets?
Gas: stimulatory; will induce cyclic AMP (second messenger) from adenylyl cyclase which will activate PKA
Gai: inhibitory
Gaq
CFTR
activated by PKA in epithelial cells which induces sodium in cell to bring fluid into lumen
What if both Gas and Gai are activated?
Cells knows which one to choose by which ligand has more concentration; may depend on number of receptors of each type
Family of G protein involved in myocardial hypertrophy
-Gq-G11 included in angiotensin receptor and endothelin receptor to induce hypertrophy via activation of downstream effectors
How are multiple signal integrated?
- multiple phosphorylations of a target
- Phosphorylation can activate a protein but sometimes you need more than one signal to activate the phosphorylation
Neoplasm
unregulated growth of cells, growing faster or more than they should
Tumor
a collection of cells that have mutations making them non-functional, can present in new growth or lump
Leukemia
Cancer of the cells in the blood that help fight infection
Dysplasia
- abnormal formation of cells in body
- Disordered growth, abnormal differentiation or proliferation of cell
- Cell does not differentiate appropriately
Myeloproliferative
increase in production in one of the types of cells from the blood
Myeloid neoplasm
Genetic abnormality that causes problem with proliferation or differentiation
Acute leukemia
Increase only in proliferating, cannot differentiate; predominately an increase in immature cells
Chronic myeloproliferative disorder
Increased proliferation but can differentiate; will have increase in all cells, immature and mature
myelodysplastic syndrome
able to differentiate but do so abnormally
Leukocytosis with neutrophilia causes
- infection (20,000 or less WBC, unless C.diff 50,000)
- leukemia (more than 20,000 WBC)
- others
When is it pertinent to differentiate bands from neutrophils?
NICU
Should you be worried if there is low lymphocytes on WBC differential?
- if it is in percentage then no because absolute number would most likely be normal; would not be considered lymphopenia
Essential Thrombocytosis
- mature platelets that are over produced
- Would see tons of platelets in blood smear
- would see more megakaryoctes in bone marrow, not usually in blood
- confirmatory test: Would look for Jak2 mutation