cell bio lecture 13

What is signal transduction? 🔄

Signal transduction is the process where cells convert signals (like hormones or growth factors) into specific cellular responses using proteins and signaling pathways 📡

Why is protein localization important in signaling? 📍

Protein location controls who it can interact with; moving a protein to a membrane can switch signals on or off by changing its access to activators (e.g GTP) ⚙

Why are membranes important for signal transduction? 🧱

Membranes concentrate proteins in a small space, increasing reaction efficiency and making signaling faster and more specific 🚀

How much can membrane translocation increase protein concentration? 📈

Membrane translocation can increase local protein concentration by about 700-fold, greatly boosting signaling efficiency ⚡

What is membrane translocation? 🚚

Membrane translocation is when a protein moves from the cytosol to a membrane to activate or change signaling output 🔁

Why does membrane translocation act like a molecular switch? 🔘

Because A PROTEINmoving to or away from a membrane rapidly changes whether a protein can signal or not ⏱

What are lipid modifications? 🧪

Lipid modifications are chemical additions

that attach proteins to membranes,

helping control where signaling happens 🧬

What is myristoylation? 🧷

Myristoylation is the irreversible addition of a myristate lipid to the N-terminus of a protein to help it bind membranes 🔒

When can myristoylation occur? ⏰

Myristoylation can happen during protein synthesis or later, such as during apoptosis after protein cleavage 💀

What is prenylation? 🔗

Prenylation is the attachment of lipid groups (farnesyl or geranylgeranyl) to CAAX-motif proteins to target them to membranes 🧲

Which proteins are commonly prenylated? 🧬

Ras family proteins are classic examples of prenylated signaling proteins involved in growth and cancer 🔥

What enzymes are involved in prenylation? ⚙️

FTase, GGTase I, RCE1, and ICMT work together to attach and process prenyl groups 🛠️

Why is prenylation clinically important? 🏥

Prenylation is targeted in cancer and progeria treatments using FTase inhibitors 💊

What is palmitoylation? 🧠

Palmitoylation is a reversible lipid modification that strengthens membrane binding and allows dynamic regulation 🔄

Why are multiple membrane interactions often needed? 🧩

One lipid anchor is usually too weak, so proteins use multiple interactions for stable membrane attachment ⚖️

What is a phospho-switch? 🔁

A phospho-switch is when phosphorylation changes a protein’s charge or location, turning signaling on or off ⚡

How does phosphorylation affect membrane binding? ⚡

Phosphorylation adds negative charge, which can weaken membrane interactions and cause protein relocalization 🚦

Why is an important feature in KRas ? 🧬

KRas shows how the same protein can cause opposite outcomes depending on where it is in the cell 🔄

What happens when KRas is at the Cell membrane? 📍

KRas at the plasma membrane promotes cell growth and proliferation 📈

What other membranes does Kras bind to and What happens when KRas relocates to other membranes? 🧨

When phosphorylated and relocated to the Golgi or mitochondria, KRas can trigger apoptosis 💀

Why are KRas mutations common in cancer? 🚨

Mutations lock KRas in an active state, causing uncontrolled growth signaling 🔥

What is membrane sequestration? 🔒

Membrane sequestration is when proteins are held at membranes to prevent signaling until they are released 🎯

Why is sequestration useful for cells? 🧠

It allows precise control by blocking access to substrates or partners until the right signal occurs ⏳

What is phosphorylation? 🧪

Phosphorylation is the addition of a phosphate group to a protein, changing its activity, location, or interactions 🔄

Why is phosphorylation a powerful regulatory mechanism? ⚡

It is fast, reversible, and highly specific, making it ideal for dynamic signaling control ⏱️

Who are the “writers” in phosphorylation signaling? ✍️

Protein kinases add phosphate groups to proteins to change their behavior 🧠

Who are the “erasers” in phosphorylation signaling? 🧽

Protein phosphatases remove phosphate groups to turn signals off 🔕

Who are the “readers” in phosphorylation signaling? 👀

SH2 , 14-3-3, PIN 1 =Reader proteins recognize phosphorylated sites and translate them into cellular responses 📖

What does phosphorylation change in proteins? 🔧

Phosphorylation can change protein shape, location, stability, and interaction networks 🧬

Why are post-translational modifications combinatorial? 🧩

Multiple PTMs act together to fine-tune signaling outcomes rather than working alone 🎛️

Why is p53 a good example of PTM integration? 🧠

p53 uses many PTMs to decide how a cell responds to stress, such as repair or apoptosis 🚦

Why is mutational analysis important in signaling studies? 🧬

It links specific amino acids to localization and function, proving cause-and-effect 🔍

What is the main takeaway of this lecture? 🎯

Where a protein is and how it is modified can be just as important as what the protein is 🧠